Author: "CERFACS" - Searchworks@Jio Institute Digital Library Search Results

Your search keyword '"CERFACS"' showing total 966 results

Start Over Author "CERFACS"

966 results on '"CERFACS"'

301. Intense storm activity during the Little Ice Age on the French Mediterranean coast

Author: Christophe Cassou, Laurent Dezileau, Philippe Martinez, Philippe Blanchemanche, Jérôme Castaings, Baptiste Joly, Pierre Sabatier, Didier Swingedouw, U. von Grafenstein, Risques (Géosciences Montpellier), Géosciences Montpellier, Université des Antilles et de la Guyane (UAG)-Institut national des sciences de l'Univers (INSU - CNRS)-Université de Montpellier (UM)-Centre National de la Recherche Scientifique (CNRS)-Université des Antilles et de la Guyane (UAG)-Institut national des sciences de l'Univers (INSU - CNRS)-Université de Montpellier (UM)-Centre National de la Recherche Scientifique (CNRS), Université des Antilles et de la Guyane (UAG)-Institut national des sciences de l'Univers (INSU - CNRS)-Université de Montpellier (UM)-Centre National de la Recherche Scientifique (CNRS), Environnements, Dynamiques et Territoires de la Montagne (EDYTEM), Centre National de la Recherche Scientifique (CNRS)-Université Savoie Mont Blanc (USMB [Université de Savoie] [Université de Chambéry]), Archéologie des Sociétés Méditerranéennes (ASM), Université Paul-Valéry - Montpellier 3 (UPVM)-Centre National de la Recherche Scientifique (CNRS)-Ministère de la Culture (MC), Centre Européen de Recherche et de Formation Avancée en Calcul Scientifique (CERFACS), CERFACS, Environnements et Paléoenvironnements OCéaniques (EPOC), Observatoire aquitain des sciences de l'univers (OASU), Université Sciences et Technologies - Bordeaux 1-Institut national des sciences de l'Univers (INSU - CNRS)-Centre National de la Recherche Scientifique (CNRS)-Université Sciences et Technologies - Bordeaux 1-Institut national des sciences de l'Univers (INSU - CNRS)-Centre National de la Recherche Scientifique (CNRS)-École pratique des hautes études (EPHE), Université Paris sciences et lettres (PSL)-Université Paris sciences et lettres (PSL)-Centre National de la Recherche Scientifique (CNRS), Laboratoire des Sciences du Climat et de l'Environnement [Gif-sur-Yvette] (LSCE), Institut national des sciences de l'Univers (INSU - CNRS)-Université Paris-Saclay-Centre National de la Recherche Scientifique (CNRS)-Commissariat à l'énergie atomique et aux énergies alternatives (CEA)-Université de Versailles Saint-Quentin-en-Yvelines (UVSQ), Géochrononologie Traceurs Archéométrie (GEOTRAC), Institut national des sciences de l'Univers (INSU - CNRS)-Université Paris-Saclay-Centre National de la Recherche Scientifique (CNRS)-Commissariat à l'énergie atomique et aux énergies alternatives (CEA)-Université de Versailles Saint-Quentin-en-Yvelines (UVSQ)-Institut national des sciences de l'Univers (INSU - CNRS)-Université Paris-Saclay-Centre National de la Recherche Scientifique (CNRS)-Commissariat à l'énergie atomique et aux énergies alternatives (CEA)-Université de Versailles Saint-Quentin-en-Yvelines (UVSQ), Glaces et Continents, Climats et Isotopes Stables (GLACCIOS), Risques ( Géosciences Montpellier ), Université des Antilles et de la Guyane ( UAG ) -Institut national des sciences de l'Univers ( INSU - CNRS ) -Université de Montpellier ( UM ) -Centre National de la Recherche Scientifique ( CNRS ) -Université des Antilles et de la Guyane ( UAG ) -Institut national des sciences de l'Univers ( INSU - CNRS ) -Université de Montpellier ( UM ) -Centre National de la Recherche Scientifique ( CNRS ), Université des Antilles et de la Guyane ( UAG ) -Institut national des sciences de l'Univers ( INSU - CNRS ) -Université de Montpellier ( UM ) -Centre National de la Recherche Scientifique ( CNRS ), Environnements, Dynamiques et Territoires de la Montagne ( EDYTEM ), Université Savoie Mont Blanc ( USMB [Université de Savoie] [Université de Chambéry] ) -Centre National de la Recherche Scientifique ( CNRS ), Archéologie des Sociétés Méditerranéennes ( ASM ), Université Paul-Valéry - Montpellier 3 ( UM3 ) -Ministère de la Culture et de la Communication ( MCC ) -Centre National de la Recherche Scientifique ( CNRS ), Centre Européen de Recherche et de Formation Avancée en Calcul Scientifique ( CERFACS ), Environnements et Paléoenvironnements OCéaniques ( EPOC ), Observatoire aquitain des sciences de l'univers ( OASU ), Université Sciences et Technologies - Bordeaux 1-Institut national des sciences de l'Univers ( INSU - CNRS ) -Centre National de la Recherche Scientifique ( CNRS ) -Université Sciences et Technologies - Bordeaux 1-Institut national des sciences de l'Univers ( INSU - CNRS ) -Centre National de la Recherche Scientifique ( CNRS ) -École pratique des hautes études ( EPHE ) -Centre National de la Recherche Scientifique ( CNRS ), Laboratoire des Sciences du Climat et de l'Environnement [Gif-sur-Yvette] ( LSCE ), Université de Versailles Saint-Quentin-en-Yvelines ( UVSQ ) -Commissariat à l'énergie atomique et aux énergies alternatives ( CEA ) -Université Paris-Saclay-Centre National de la Recherche Scientifique ( CNRS ), Environnements, Dynamiques et Territoires de Montagne (EDYTEM), Université Savoie Mont Blanc (USMB [Université de Savoie] [Université de Chambéry])-Centre National de la Recherche Scientifique (CNRS), Université Sciences et Technologies - Bordeaux 1 (UB)-Institut national des sciences de l'Univers (INSU - CNRS)-Centre National de la Recherche Scientifique (CNRS)-Université Sciences et Technologies - Bordeaux 1 (UB)-Institut national des sciences de l'Univers (INSU - CNRS)-Centre National de la Recherche Scientifique (CNRS)-École Pratique des Hautes Études (EPHE), Université de Versailles Saint-Quentin-en-Yvelines (UVSQ)-Commissariat à l'énergie atomique et aux énergies alternatives (CEA)-Institut national des sciences de l'Univers (INSU - CNRS)-Université Paris-Saclay-Centre National de la Recherche Scientifique (CNRS), and Université de Versailles Saint-Quentin-en-Yvelines (UVSQ)-Commissariat à l'énergie atomique et aux énergies alternatives (CEA)-Institut national des sciences de l'Univers (INSU - CNRS)-Université Paris-Saclay-Centre National de la Recherche Scientifique (CNRS)-Université de Versailles Saint-Quentin-en-Yvelines (UVSQ)-Commissariat à l'énergie atomique et aux énergies alternatives (CEA)-Institut national des sciences de l'Univers (INSU - CNRS)-Université Paris-Saclay-Centre National de la Recherche Scientifique (CNRS)
Subjects: Mediterranean climate, 010504 meteorology & atmospheric sciences, [SDE.MCG]Environmental Sciences/Global Changes, animal diseases, Climate change, 010502 geochemistry & geophysics, Oceanography, 01 natural sciences, Mediterranean sea, Storm, Paleoclimatology, Mediterranean Sea, 14. Life underwater, Overwash, Ecology, Evolution, Behavior and Systematics, 0105 earth and related environmental sciences, Earth-Surface Processes, Paleontology, Sediment, Lagoon, [ SDE.MCG ] Environmental Sciences/Global Changes, Risk assessments, [SDU.STU.CL]Sciences of the Universe [physics]/Earth Sciences/Climatology, 13. Climate action, North Atlantic oscillation, Little Ice Age, [ SDU.STU.CL ] Sciences of the Universe [physics]/Earth Sciences/Climatology, North Atlantic Oscillation, Geology
Abstract: International audience; Understanding long-term variability in the frequency of intense storm activity is important for assessing whether changes are controlled by climate evolution. Understanding this variability is also important for predicting present and future community vulnerability and economic loss. Our ability to make these assessments has been limited by the short (less than 50 years) instrument record of storm activity. Storm-induced deposits preserved in the sediments of coastal lagoons offer the opportunity to study the links between climatic conditions and storm activity on longer timescales. In this study, we present a record of these extreme climatic events that have occurred in the French Mediterrannean coast over the past 1500 years. The identification of these extreme events is based on the analysis of sediment cores from Gulf of Aigues-Mortes lagoons that contain a specific sedimentary and geochemical signature associated with intense storms.;Overwash deposits do not show any evidence of intense storm landfalls in the region for several hundred years prior to the late 17th century A.D. The apparent increase in intense storms around 250 years ago occurs during the latter half of the Little Ice Age, a time of lower continental surface temperatures. Comparison of the sediment record with palaeoclimate records indicates that this variability was probably modulated by atmospheric dynamics. The apparent increase of the superstorm activity during the latter half of the Little Ice Age was probably due to the thermal gradient increase leading to enhanced lower tropospheric baroclinicity over a large Central Atlantic/European domain and leading to a modification of the occurrence of extreme wind events along the French Mediterranean coast. A complete understanding of the relationship between climate fluctuations, storm activity, and the coastal response will be crucial to predicting the impacts of future climate change.
Published: 2011

302. Interdecadal changes in SST variability drivers in the Senegalese-upwelling: the impact of ENSO

Author: Malick Wade, Belén Rodríguez-Fonseca, Marta Martín-Rey, Alban Lazar, Jorge López-Parages, Amadou Thierno Gaye, Laboratoire de Physique de l'Atmosphère et de l'Océan Siméon Fongang (LPAO-SF), École Supérieure Polytechnique de Dakar (ESP), Université Cheikh Anta Diop [Dakar, Sénégal] (UCAD)-Université Cheikh Anta Diop [Dakar, Sénégal] (UCAD), Instituto de Geociencias [Madrid] (IGEO), Universidad Complutense de Madrid = Complutense University of Madrid [Madrid] (UCM)-Consejo Superior de Investigaciones Científicas [Madrid] (CSIC), Universidad Complutense de Madrid = Complutense University of Madrid [Madrid] (UCM), Instituto de Ciencias del Mar de Barcelona (ICM), Consejo Superior de Investigaciones Científicas [Madrid] (CSIC), Océan et variabilité du climat (VARCLIM), Laboratoire d'Océanographie et du Climat : Expérimentations et Approches Numériques (LOCEAN), Muséum national d'Histoire naturelle (MNHN)-Institut de Recherche pour le Développement (IRD)-Institut national des sciences de l'Univers (INSU - CNRS)-Sorbonne Université (SU)-Centre National de la Recherche Scientifique (CNRS)-Institut Pierre-Simon-Laplace (IPSL (FR_636)), École normale supérieure - Paris (ENS-PSL), Université Paris sciences et lettres (PSL)-Université Paris sciences et lettres (PSL)-Université de Versailles Saint-Quentin-en-Yvelines (UVSQ)-Commissariat à l'énergie atomique et aux énergies alternatives (CEA)-Institut national des sciences de l'Univers (INSU - CNRS)-École polytechnique (X)-Centre National d'Études Spatiales [Toulouse] (CNES)-Sorbonne Université (SU)-Centre National de la Recherche Scientifique (CNRS)-Université Paris Cité (UPCité)-École normale supérieure - Paris (ENS-PSL), Université Paris sciences et lettres (PSL)-Université Paris sciences et lettres (PSL)-Université de Versailles Saint-Quentin-en-Yvelines (UVSQ)-Commissariat à l'énergie atomique et aux énergies alternatives (CEA)-École polytechnique (X)-Centre National d'Études Spatiales [Toulouse] (CNES)-Sorbonne Université (SU)-Centre National de la Recherche Scientifique (CNRS)-Université Paris Cité (UPCité)-Muséum national d'Histoire naturelle (MNHN)-Institut de Recherche pour le Développement (IRD)-Institut national des sciences de l'Univers (INSU - CNRS)-Sorbonne Université (SU)-Centre National de la Recherche Scientifique (CNRS)-Institut Pierre-Simon-Laplace (IPSL (FR_636)), Université Paris sciences et lettres (PSL)-Université Paris sciences et lettres (PSL)-Université de Versailles Saint-Quentin-en-Yvelines (UVSQ)-Commissariat à l'énergie atomique et aux énergies alternatives (CEA)-École polytechnique (X)-Centre National d'Études Spatiales [Toulouse] (CNES)-Sorbonne Université (SU)-Centre National de la Recherche Scientifique (CNRS)-Université Paris Cité (UPCité), Centre Européen de Recherche et de Formation Avancée en Calcul Scientifique (CERFACS), Universidad de Málaga [Málaga] = University of Málaga [Málaga], Ministerio de Ciencia, Innovación y Universidades (España), European Commission, and Agencia Estatal de Investigación (España)
Subjects: Interannual teleconnection, Atmospheric Science, Eastern North Tropical Atlantic, [PHYS.PHYS.PHYS-GEO-PH]Physics [physics]/Physics [physics]/Geophysics [physics.geo-ph], Senegalese upwelling, ENSO
Abstract: 19 pages, 11 figures, 1 table, supplementary information https://doi.org/10.1007/s00382-022-06311-3.-- Data availability: Enquiries about data availability should be directed to the authors, Sea surface temperature (SST) variability in the North Eastern Tropical Atlantic has its center of action in the Senegalese–Mauritanian upwelling system, where its drivers are wind-induced ocean dynamics and air–sea thermodynamic processes. Thus, a better understanding of the local wind variations, together with their predictability, contributes to a more comprehensive assessment of the SST variability in that region. In this study, we use monthly data from two ocean reanalyses, SODA and ORAS-5, and a regional forced-ocean simulation to characterize the interannual SST variability off the Senegalese Coast in the common period 1960–2008. Local indices of the mixed layer heat budget during the major upwelling season (February–March–April) exhibit pronounced interannual to decadal variability. We demonstrate that the local interannual SST variability undergoes inter-decadal fluctuation and concomitant changes in its local and remote drivers. Off-Senegal SST variability was largely controlled by wind-induced Ekman transport during the 1960s–1970s, acting under favorable thermocline and mixed layer conditions. However, from 1980s onwards, the drastically reduced Ekman impact observed on local SSTs is associated with a deeper thermocline. This shift in the effectiveness of the dynamic mechanisms coincides with a more active ENSO teleconnection with upwelling before the 1980s. An extended SODA record reveals that the multidecadal modulator of the ENSO impact on the North-eastern Tropical Atlantic resembles the negative phase of the Atlantic Multidecadal Variability. Our results bring to light the fundamental role played by the global decadal background state in the activation of the drivers and air-sea mechanisms responsible for generating the interannual off-Senegal SST variability, With the institutional support of the ‘Severo Ochoa Centre of Excellence’ accreditation (CEX2019-000928-S), The research leading to these results has received funding from the CSIC ICOOP projects: ICOOPB20204, ICOOPB20358 (the UCM Cooperation Project from XIV and XVII calls); the Spanish Project CGL2017-86415-R; the EU/FP7 PREFACE (Grant Agreement 603521). [...] MMR received funding from the MSCA-IF-EF-ST FESTIVAL (H2020-EU project 797236) and from a Juan de la Cierva Incorporation (IJC2019-041150-I) research contract of MICINN (Spain). This work was also supported by the TRIATLAS project, which has received funding from the European Union’s Horizon 2020 research and innovation program under Grant agreement No 817578
Published: 2022

303. A past discharges assimilation system for ensemble streamflow forecasts over France – Part 1: Description and validation of the assimilation system

Author: Sebastien Massart, Eric Martin, Guillaume Thirel, Jean-François Mahfouf, Sophie Ricci, Florence Habets, Groupe d'étude de l'atmosphère météorologique (CNRM-GAME), Institut national des sciences de l'Univers (INSU - CNRS)-Météo France-Centre National de la Recherche Scientifique (CNRS), JRC Institute for Environment and Sustainability (IES), European Commission - Joint Research Centre [Ispra] (JRC), Centre Européen de Recherche et de Formation Avancée en Calcul Scientifique (CERFACS), CERFACS, Centre de Géosciences (GEOSCIENCES), MINES ParisTech - École nationale supérieure des mines de Paris, Université Paris sciences et lettres (PSL)-Université Paris sciences et lettres (PSL), Centre national de recherches météorologiques (CNRM), Institut national des sciences de l'Univers (INSU - CNRS)-Observatoire Midi-Pyrénées (OMP), Institut de Recherche pour le Développement (IRD)-Université Toulouse III - Paul Sabatier (UT3), Université de Toulouse (UT)-Université de Toulouse (UT)-Institut national des sciences de l'Univers (INSU - CNRS)-Centre National d'Études Spatiales [Toulouse] (CNES)-Centre National de la Recherche Scientifique (CNRS)-Météo-France -Institut de Recherche pour le Développement (IRD)-Université Toulouse III - Paul Sabatier (UT3), Université de Toulouse (UT)-Université de Toulouse (UT)-Institut national des sciences de l'Univers (INSU - CNRS)-Centre National d'Études Spatiales [Toulouse] (CNES)-Centre National de la Recherche Scientifique (CNRS)-Météo-France -Centre National de la Recherche Scientifique (CNRS), and Mines Paris - PSL (École nationale supérieure des mines de Paris)
Subjects: State variable, 010504 meteorology & atmospheric sciences, Meteorology, [SDE.MCG]Environmental Sciences/Global Changes, 0207 environmental engineering, 02 engineering and technology, Best linear unbiased prediction, 01 natural sciences, lcsh:Technology, lcsh:TD1-1066, Hydraulic conductivity, Streamflow, Hydrometeorology, lcsh:Environmental technology. Sanitary engineering, 020701 environmental engineering, lcsh:Environmental sciences, 0105 earth and related environmental sciences, lcsh:GE1-350, Moisture, lcsh:T, lcsh:Geography. Anthropology. Recreation, 6. Clean water, lcsh:G, 13. Climate action, Soil water, Soil horizon
Abstract: Two Ensemble Streamflow Prediction Systems (ESPSs) have been set up at Météo-France. They are based on the French SIM distributed hydrometeorological model. A deterministic analysis run of SIM is used to initialize the two ESPSs. In order to obtain a better initial state, a past discharges assimilation system has been implemented into this analysis SIM run, using the Best Linear Unbiased Estimator (BLUE). Its role is to improve the model soil moisture by using streamflow observations in order to better simulate streamflow. The skills of the assimilation system were assessed for a 569-day period on six different configurations, including two different physics schemes of the model (the use of an exponential profile of hydraulic conductivity or not) and, for each one, three different ways of considering the model soil moisture in the BLUE state variables. Respect of the linearity hypothesis of the BLUE was verified by assessing of the impact of iterations of the BLUE. The configuration including the use of the exponential profile of hydraulic conductivity and the combination of the moisture of the two soil layers in the state variable showed a significant improvement of streamflow simulations. It led to a significantly better simulation than the reference one, and the lowest soil moisture corrections. These results were confirmed by the study of the impacts of the past discharge assimilation system on a set of 49 independent stations., JRC.H.7-Climate Risk Management
Published: 2010

304. A two-step chemical scheme for kerosene–air premixed flames

Author: Thierry Poinsot, Eleonore Riber, Marlène Sanjosé, Benedetta Franzelli, Centre Européen de Recherche et de Formation Avancée en Calcul Scientifique (CERFACS), CERFACS, Institut de mécanique des fluides de Toulouse (IMFT), Université Toulouse III - Paul Sabatier (UT3), Université Fédérale Toulouse Midi-Pyrénées-Université Fédérale Toulouse Midi-Pyrénées-Centre National de la Recherche Scientifique (CNRS)-Institut National Polytechnique (Toulouse) (Toulouse INP), and Université Fédérale Toulouse Midi-Pyrénées
Subjects: Premixed flame, Laminar flame speed, business.industry, Chemistry, [SPI.FLUID]Engineering Sciences [physics]/Reactive fluid environment, 020209 energy, General Chemical Engineering, General Physics and Astronomy, Energy Engineering and Power Technology, Thermodynamics, Context (language use), Laminar flow, 02 engineering and technology, General Chemistry, Flame speed, Combustion, 01 natural sciences, 7. Clean energy, 010305 fluids & plasmas, Fuel Technology, 0103 physical sciences, 0202 electrical engineering, electronic engineering, information engineering, Exhaust gas recirculation, business, Large eddy simulation
Abstract: International audience; A reduced two-step scheme (called 2S KERO BFER) for kerosene-air premixed flames is presented in the context of Large Eddy Simulation of reacting turbulent flows in industrial applications. The chemical mechanism is composed of two re- actions corresponding to the fuel oxidation into CO and H2O, and the CO − CO2 equilibrium. To ensure the validity of the scheme for rich combustion, the pre- exponential constants of the two reactions are tabulated versus the local equiva- lence ratio. The fuel and oxidizer exponents are chosen to guarantee the correct dependence of laminar flame speed with pressure. Due to a lack of experimen- tal results, the detailed mechanism of Dagaut composed of 209 species and 1673 reactions, and the skeletal mechanism of Luche composed of 91 species and 991 reactions have been used to validate the reduced scheme. Computations of one- dimensional laminar flames have been performed with the 2S KERO BFER scheme using the CANTERA and COSILAB softwares for a wide range of pressure ([1;12] atm), fresh gas temperature ([300;700] K), and equivalence ratio ([0.6;2.0]). Results show that the flame speed is correctly predicted for the whole range of parameters, showing a maximum for stoichiometric flames, a decrease for rich combustion and a satisfactory pressure dependence. The burnt gas temperature and the dilution by Exhaust Gas Recirculation are also well reproduced. Moreover, the results for ignition delay time are in good agreement with the experiments.
Published: 2010

305. A linear CO chemistry parameterization in a chemistry-transport model: evaluation and application to data assimilation

Author: Nathaniel J. Livesey, Jean-Luc Attié, Béatrice Josse, H. Teyssèdre, L. El Amraoui, Sebastien Massart, David P. Edwards, Philippe Ricaud, Hugh C. Pumphrey, Daniel Cariolle, Andrea Piacentini, Jean-Pierre Cammas, Vincent-Henri Peuch, M. Claeyman, Laboratoire d'aérologie (LAERO), Centre National de la Recherche Scientifique (CNRS)-Observatoire Midi-Pyrénées (OMP), Météo France-Centre National d'Études Spatiales [Toulouse] (CNES)-Université Fédérale Toulouse Midi-Pyrénées-Centre National de la Recherche Scientifique (CNRS)-Institut de Recherche pour le Développement (IRD)-Météo France-Centre National d'Études Spatiales [Toulouse] (CNES)-Université Fédérale Toulouse Midi-Pyrénées-Centre National de la Recherche Scientifique (CNRS)-Institut de Recherche pour le Développement (IRD)-Université Toulouse III - Paul Sabatier (UT3), Université Fédérale Toulouse Midi-Pyrénées, Groupe d'étude de l'atmosphère météorologique (CNRM-GAME), Institut national des sciences de l'Univers (INSU - CNRS)-Météo France-Centre National de la Recherche Scientifique (CNRS), Centre Européen de Recherche et de Formation Avancée en Calcul Scientifique (CERFACS), CERFACS, Météo France, Jet Propulsion Laboratory (JPL), California Institute of Technology (CALTECH)-NASA, University of Edinburgh, National Center for Atmospheric Research [Boulder] (NCAR), The publication of this article is financed by CNRS-INSU, Université Toulouse III - Paul Sabatier (UT3), Université de Toulouse (UT)-Université de Toulouse (UT)-Observatoire Midi-Pyrénées (OMP), Institut de Recherche pour le Développement (IRD)-Université Toulouse III - Paul Sabatier (UT3), Université de Toulouse (UT)-Université de Toulouse (UT)-Institut national des sciences de l'Univers (INSU - CNRS)-Centre National d'Études Spatiales [Toulouse] (CNES)-Centre National de la Recherche Scientifique (CNRS)-Météo-France -Institut de Recherche pour le Développement (IRD)-Institut national des sciences de l'Univers (INSU - CNRS)-Centre National d'Études Spatiales [Toulouse] (CNES)-Centre National de la Recherche Scientifique (CNRS)-Météo-France -Centre National de la Recherche Scientifique (CNRS), Centre national de recherches météorologiques (CNRM), Institut national des sciences de l'Univers (INSU - CNRS)-Observatoire Midi-Pyrénées (OMP), Université de Toulouse (UT)-Université de Toulouse (UT)-Institut national des sciences de l'Univers (INSU - CNRS)-Centre National d'Études Spatiales [Toulouse] (CNES)-Centre National de la Recherche Scientifique (CNRS)-Météo-France -Institut de Recherche pour le Développement (IRD)-Université Toulouse III - Paul Sabatier (UT3), Université de Toulouse (UT)-Université de Toulouse (UT)-Institut national des sciences de l'Univers (INSU - CNRS)-Centre National d'Études Spatiales [Toulouse] (CNES)-Centre National de la Recherche Scientifique (CNRS)-Météo-France -Centre National de la Recherche Scientifique (CNRS), Météo-France Direction Interrégionale Sud-Est (DIRSE), Météo-France, and NASA-California Institute of Technology (CALTECH)
Subjects: Atmospheric Science, Meteorology, Chemical transport model, 010504 meteorology & atmospheric sciences, 010501 environmental sciences, Atmospheric sciences, 010502 geochemistry & geophysics, 01 natural sciences, 7. Clean energy, MOPITT, Troposphere, lcsh:Chemistry, Data assimilation, Ozone layer, GENERAL-CIRCULATION MODEL, CARBON-MONOXIDE, Stratosphere, 0105 earth and related environmental sciences, [PHYS.PHYS.PHYS-AO-PH]Physics [physics]/Physics [physics]/Atmospheric and Oceanic Physics [physics.ao-ph], UPPER TROPOSPHERE, Chemistry, STRATOSPHERIC OZONE, ODIN/SMR, NITROUS-OXIDE, ATMOSPHERE, SIMULATIONS, lcsh:QC1-999, Microwave Limb Sounder, lcsh:QD1-999, 13. Climate action, BIOMASS BURNING EMISSIONS, Water vapor, lcsh:Physics, OZONE PHOTOCHEMISTRY PARAMETERIZATION
Abstract: This paper presents an evaluation of a new linear parameterization valid for the troposphere and the stratosphere, based on a first order approximation of the carbon monoxide (CO) continuity equation. This linear scheme (hereinafter noted LINCO) has been implemented in the 3-D Chemical Transport Model (CTM) MOCAGE of Météo-France. On the one hand, a one and a half years of LINCO simulation has been compared to output obtained from a detailed chemical scheme output. In spite of small differences, the seasonal and global CO distributions obtained by both schemes present similar general characteristics. The mean differences between both schemes remain small within about ±25 ppbv (part per billion by volume) in the troposphere and ±15 ppbv in the stratosphere. On the other hand, LINCO has been compared to diverse observations from satellite instruments covering the troposphere (Measurements Of Pollution In The Troposphere: MOPITT) and the stratosphere (Microwave Limb Sounder: MLS) and also from aircraft (Measurements of ozone and water vapour by Airbus in-service aircraft: MOZAIC programme) mostly flying in the upper troposphere and lower stratosphere. A good agreement is generally found in the troposphere and the lower stratosphere. In the troposphere, the LINCO seasonal variations as well as the vertical and horizontal distributions are quite close to MOPITT CO observations. However, a bias of ~−40 ppbv is observed at 700 hPa between LINCO and MOPITT which is probably caused by too low emission values. In the stratosphere, MLS and LINCO present similar large-scale patterns, except over the poles where the CO concentration is underestimated by the model. We suggest that the underestimation of CO at polar latitudes is not related to the linear scheme but is induced by a too rapid transport by the meridional circulation. In the UTLS (Upper Troposphere Lower Stratosphere), LINCO tends to slightly overestimate the MOZAIC aircraft observations, with general small biases less than 2%. LINCO is a simple parameterization compared to a detailed chemical scheme, allowing very fast calculations and thus making possible long reanalyses of MOPITT CO data. The computational cost just corresponds to the transport of an additional passive tracer. For this, we used a variational 3-D-FGAT (First Guess at Appropriate Time) method in conjunction with MOCAGE for a long run of one and a half years. The data assimilation greatly improves the vertical CO distribution in the troposphere from 700 to 350 hPa compared to independent MOZAIC profiles. At 146 hPa, the assimilated CO 2-D distribution is improved compared to MLS observations by reducing the bias up to a factor of 2 in the tropics. At extratropical latitudes, the assimilated fields tend to underestimate the CO concentrations resulting from an excessive equator to pole circulation. This study confirms that the linear scheme is able to simulate reasonably well the CO distribution in the troposphere and in the lower stratosphere. Therefore, the low computing cost of the linear scheme opens new perspectives to make free runs and CO data assimilation runs at high resolution and over periods of several years.
Published: 2010

306. Extended integral wall-model for large-eddy simulations of compressible wall-bounded turbulent flows

Author: Dimitrios Papadogiannis, J.-F Boussuge, Jean-François Boussuge, Marc Montagnac, Mathieu Catchirayer, Xavier Garnaud, Pierre Sagaut, Centre Européen de Recherche et de Formation Avancée en Calcul Scientifique (CERFACS), Safran Tech, Laboratoire de Mécanique, Modélisation et Procédés Propres (M2P2), Aix Marseille Université (AMU)-École Centrale de Marseille (ECM)-Centre National de la Recherche Scientifique (CNRS), Laboratoire d'hydrodynamique (LadHyX), École polytechnique (X)-Centre National de la Recherche Scientifique (CNRS), Safran Aircraft Engines, Association Nationale de la Recherche et de la Technologie (ANRT) 2015/0193, ANR-06-NEUR-0048,TGV-DORIT,LES SYSTÈMES GLUTAMATERGIQUES DANS LES MALADIES NEUROLOGIQUES ET PSYCHIATRIQUES(2006), CERFACS, CERFACS [Toulouse], Institut national des sciences de l'Univers (INSU - CNRS)-Centre National de la Recherche Scientifique (CNRS), and Centre National de la Recherche Scientifique (CNRS)-École Centrale de Marseille (ECM)-Aix Marseille Université (AMU)
Subjects: Computational Mechanics, Direct numerical simulation, Layer Models, 02 engineering and technology, 01 natural sciences, Compressible flow, Channel Flow, 010305 fluids & plasmas, Physics::Fluid Dynamics, [SPI]Engineering Sciences [physics], symbols.namesake, 0203 mechanical engineering, 0103 physical sciences, [PHYS.MECA.MEFL]Physics [physics]/Mechanics [physics]/Fluid mechanics [physics.class-ph], Boundary value problem, Adverse Pressure-Gradient, Fluid Flow and Transfer Processes, Physics, Turbulence, Mechanical Engineering, Heat-Transfer, Temperature, Laminar flow, [PHYS.MECA]Physics [physics]/Mechanics [physics], Mechanics, Condensed Matter Physics, Integral equation, Boundary layer, Subgrid-Scale Model, Outer Layer, 020303 mechanical engineering & transports, Mach number, Mechanics of Materials, LES, symbols, Direct Numerical-Simulation, Guide Vane
Abstract: International audience; Wall-modeling is required to make large-eddy simulations of high-Reynolds number wall-bounded turbulent flows feasible in terms of computational cost. Here, an extension of the integral wall-model for large-eddy simulations (iWMLESs) for incompressible flows developed by Yang et al. ["Integral wall model for large eddy simulations of wall-bounded turbulent flows," Phys. Fluids 27(2), 025112 (2015)] to compressible and isothermal flows is proposed and assessed. The iWMLES approach is analogous to the von Karman-Pohlhausen integral method for laminar flows: the velocity profile is parameterized, and unknown coefficients are determined by matching boundary conditions obeying the integral boundary layer momentum equation. It allows non-equilibrium effects such as pressure gradient and convection to be included at a computing cost similar to analytical wall-models. To take into account density variations and temperature gradients, the temperature profile is also parameterized and the integral compressible boundary layer energy equation is considered. Parameterized profiles are based on the usual logarithmic wall functions with corrective terms to extend their range of validity. Instead of solving a set of differential equations as wall-models based on the thin boundary layer equation approach, a simple linear system is solved. The proposed wall-model is implemented in a finite-volume cell-centered structured grid solver and assessed on adiabatic and isothermal plane channel flows at several friction Reynolds and Mach numbers. For low Mach number cases, mean profiles, wall fluxes, and turbulent fluctuations are in agreement with those of Direct Numerical Simulation (DNS). For supersonic flows, the results are in good agreement with the DNS data, especially the mean velocity quantities and the wall friction, while standard analytical wall-models show their limits.
Published: 2018

307. Corrigendum

Author: Pannekoucke, Olivier, Ricci, Sophie, Bathelemy, Sébastien, Menard, Richard, Thual, Olivier, Météo France, Centre Européen de Recherche et de Formation Avancée en Calcul Scientifique (CERFACS), CERFACS, Environment and Climate Change Canada, Institut de mécanique des fluides de Toulouse (IMFT), Université Toulouse III - Paul Sabatier (UT3), Université Fédérale Toulouse Midi-Pyrénées-Université Fédérale Toulouse Midi-Pyrénées-Centre National de la Recherche Scientifique (CNRS)-Institut National Polytechnique (Toulouse) (Toulouse INP), Université Fédérale Toulouse Midi-Pyrénées, Centre National de la Recherche Scientifique - CNRS (FRANCE), Institut National Polytechnique de Toulouse - INPT (FRANCE), Université Toulouse III - Paul Sabatier - UT3 (FRANCE), Centre Européen de Recherche et Formation Avancées en Calcul Scientifique - CERFACS (FRANCE), Environment and Climate Change Canada - ECCC (CANADA), Météo France (FRANCE), Centre Européen de Recherche et Formation Avancées en Calcul Scientifique - CERFACS (Toulouse, France), Institut de Mécanique des Fluides de Toulouse - IMFT (Toulouse, France), and Institut National Polytechnique de Toulouse - Toulouse INP (FRANCE)
Subjects: Atmospheric Science, 010504 meteorology & atmospheric sciences, Oceanography, 01 natural sciences, 010305 fluids & plasmas, Parameterisation of analysis, [CHIM.GENI]Chemical Sciences/Chemical engineering, Data assimilation, 0103 physical sciences, Génie chimique, Kalman filter, Covariance dynamics, 0105 earth and related environmental sciences
Abstract: International audience; This article refers to : Parametric Kalman filter for chemical transport models. In our previous contribution Pannekoucke et al. (2016) (P16), an error has been made in the derivation of the error diffusion tensor dynamics Eq. (20). This involves an error in the Lagrangian dynamics of the uncertainty given in the Algorithm 2, while leaving the Eulerian dyanmics unchanged. The corrigendum is organized as follows. The modification of the Lagrangian dynamics is presented in Section 2, where a new version of the Algorithm 2 of P16 is presented. The computation leading to the Eulerian dynamics is described in Section 3, which gives the dynamics presented in Eq. (26) of P16.
Published: 2018

308. Global model simulations of air pollution during the 2003 European heat wave

Author: Gilles Athier, P. Moinat, Johannes Flemming, Antje Inness, Arjo Segers, M. van Weele, Jean-Pierre Cammas, O. Stein, Vincent Huijnen, Christos Zerefos, N. Elguindi, Martin G. Schultz, Valérie Thouret, Vincent-Henri Peuch, Carlos Ordóñez, Eleni Katragkou, Harald Flentje, Laboratoire d'aérologie (LAERO), Université Toulouse III - Paul Sabatier (UT3), Université Fédérale Toulouse Midi-Pyrénées-Université Fédérale Toulouse Midi-Pyrénées-Observatoire Midi-Pyrénées (OMP), Météo France-Centre National d'Études Spatiales [Toulouse] (CNES)-Université Fédérale Toulouse Midi-Pyrénées-Centre National de la Recherche Scientifique (CNRS)-Institut de Recherche pour le Développement (IRD)-Météo France-Centre National d'Études Spatiales [Toulouse] (CNES)-Centre National de la Recherche Scientifique (CNRS)-Institut de Recherche pour le Développement (IRD)-Centre National de la Recherche Scientifique (CNRS), Observatoire Midi-Pyrénées (OMP), Météo France-Centre National d'Études Spatiales [Toulouse] (CNES)-Université Fédérale Toulouse Midi-Pyrénées-Centre National de la Recherche Scientifique (CNRS)-Institut de Recherche pour le Développement (IRD), Max Planck Institute for Meteorology (MPI-M), Max-Planck-Gesellschaft, Royal Netherlands Meteorological Institute (KNMI), European Centre for Medium-Range Weather Forecasts (ECMWF), Deutscher Wetterdienst [Offenbach] (DWD), Aristotelian University of Thessaloniki, Aristotle University of Thessaloniki, Centre Européen de Recherche et de Formation Avancée en Calcul Scientifique (CERFACS), CERFACS, Groupe d'étude de l'atmosphère météorologique (CNRM-GAME), Institut national des sciences de l'Univers (INSU - CNRS)-Météo France-Centre National de la Recherche Scientifique (CNRS), The Netherlands Organisation for Applied Scientific Research (TNO), National and Kapodistrian University of Athens (NKUA), Institute for Chemistry and Dynamics of the Geosphere (ICG), FZ Jülich, Germany, Université de Toulouse (UT)-Université de Toulouse (UT)-Observatoire Midi-Pyrénées (OMP), Institut de Recherche pour le Développement (IRD)-Université Toulouse III - Paul Sabatier (UT3), Université de Toulouse (UT)-Université de Toulouse (UT)-Institut national des sciences de l'Univers (INSU - CNRS)-Centre National d'Études Spatiales [Toulouse] (CNES)-Centre National de la Recherche Scientifique (CNRS)-Météo-France -Institut de Recherche pour le Développement (IRD)-Institut national des sciences de l'Univers (INSU - CNRS)-Centre National d'Études Spatiales [Toulouse] (CNES)-Centre National de la Recherche Scientifique (CNRS)-Météo-France -Centre National de la Recherche Scientifique (CNRS), Université de Toulouse (UT)-Université de Toulouse (UT)-Institut national des sciences de l'Univers (INSU - CNRS)-Centre National d'Études Spatiales [Toulouse] (CNES)-Centre National de la Recherche Scientifique (CNRS)-Météo-France, Centre national de recherches météorologiques (CNRM), Institut national des sciences de l'Univers (INSU - CNRS)-Observatoire Midi-Pyrénées (OMP), Université de Toulouse (UT)-Université de Toulouse (UT)-Institut national des sciences de l'Univers (INSU - CNRS)-Centre National d'Études Spatiales [Toulouse] (CNES)-Centre National de la Recherche Scientifique (CNRS)-Météo-France -Institut de Recherche pour le Développement (IRD)-Université Toulouse III - Paul Sabatier (UT3), and Université de Toulouse (UT)-Université de Toulouse (UT)-Institut national des sciences de l'Univers (INSU - CNRS)-Centre National d'Études Spatiales [Toulouse] (CNES)-Centre National de la Recherche Scientifique (CNRS)-Météo-France -Centre National de la Recherche Scientifique (CNRS)
Subjects: Pollution, Atmospheric Science, Ozone, 010504 meteorology & atmospheric sciences, media_common.quotation_subject, Air pollution, 010501 environmental sciences, Atmospheric sciences, medicine.disease_cause, 01 natural sciences, MOPITT, lcsh:Chemistry, Troposphere, chemistry.chemical_compound, ddc:550, medicine, 0105 earth and related environmental sciences, media_common, [PHYS.PHYS.PHYS-AO-PH]Physics [physics]/Physics [physics]/Atmospheric and Oceanic Physics [physics.ao-ph], Heat wave, lcsh:QC1-999, Boundary layer, lcsh:QD1-999, chemistry, 13. Climate action, Climatology, lcsh:Physics, Carbon monoxide
Abstract: Three global Chemistry Transport Models – MOZART, MOCAGE, and TM5 – as well as MOZART coupled to the IFS meteorological model including assimilation of ozone (O3) and carbon monoxide (CO) satellite column retrievals, have been compared to surface measurements and MOZAIC vertical profiles in the troposphere over Western/Central Europe for summer 2003. The models reproduce the meteorological features and enhancement of pollution during the period 2–14 August, but not fully the ozone and CO mixing ratios measured during that episode. Modified normalised mean biases are around −25% (except ~5% for MOCAGE) in the case of ozone and from −80% to −30% for CO in the boundary layer above Frankfurt. The coupling and assimilation of CO columns from MOPITT overcomes some of the deficiencies in the treatment of transport, chemistry and emissions in MOZART, reducing the negative biases to around 20%. The high reactivity and small dry deposition velocities in MOCAGE seem to be responsible for the overestimation of O3 in this model. Results from sensitivity simulations indicate that an increase of the horizontal resolution to around 1°×1° and potential uncertainties in European anthropogenic emissions or in long-range transport of pollution cannot completely account for the underestimation of CO and O3 found for most models. A process-oriented TM5 sensitivity simulation where soil wetness was reduced results in a decrease in dry deposition fluxes and a subsequent ozone increase larger than the ozone changes due to the previous sensitivity runs. However this latest simulation still underestimates ozone during the heat wave and overestimates it outside that period. Most probably, a combination of the mentioned factors together with underrepresented biogenic emissions in the models, uncertainties in the modelling of vertical/horizontal transport processes in the proximity of the boundary layer as well as limitations of the chemistry schemes are responsible for the underestimation of ozone (overestimation in the case of MOCAGE) and CO found in the models during this extreme pollution event.
Published: 2010

309. Flexible GMRES with Deflated Restarting

Author: X. Pinel, Luc Giraud, Xavier Vasseur, Serge Gratton, High-End Parallel Algorithms for Challenging Numerical Simulations (HiePACS), Laboratoire Bordelais de Recherche en Informatique (LaBRI), Université de Bordeaux (UB)-École Nationale Supérieure d'Électronique, Informatique et Radiocommunications de Bordeaux (ENSEIRB)-Centre National de la Recherche Scientifique (CNRS)-Université de Bordeaux (UB)-École Nationale Supérieure d'Électronique, Informatique et Radiocommunications de Bordeaux (ENSEIRB)-Centre National de la Recherche Scientifique (CNRS)-Inria Bordeaux - Sud-Ouest, Institut National de Recherche en Informatique et en Automatique (Inria)-Institut National de Recherche en Informatique et en Automatique (Inria), Ecole Nationale Supérieure d'Electrotechnique, d'Electronique, d'Informatique, d'Hydraulique et de Télécommunications (ENSEEIHT), Institut National Polytechnique (Toulouse) (Toulouse INP), Université de Toulouse (UT)-Université de Toulouse (UT), Centre Européen de Recherche et de Formation Avancée en Calcul Scientifique (CERFACS), Université de Bordeaux (UB)-Centre National de la Recherche Scientifique (CNRS)-École Nationale Supérieure d'Électronique, Informatique et Radiocommunications de Bordeaux (ENSEIRB)-Université de Bordeaux (UB)-Centre National de la Recherche Scientifique (CNRS)-École Nationale Supérieure d'Électronique, Informatique et Radiocommunications de Bordeaux (ENSEIRB)-Inria Bordeaux - Sud-Ouest, Université Fédérale Toulouse Midi-Pyrénées-Université Fédérale Toulouse Midi-Pyrénées, and CERFACS
Subjects: Wave propagation, Preconditioner, Applied Mathematics, Numerical technique, MathematicsofComputing_NUMERICALANALYSIS, 010103 numerical & computational mathematics, Krylov subspace, Solver, Computer Science::Numerical Analysis, 01 natural sciences, Generalized minimal residual method, Mathematics::Numerical Analysis, Computational science, 010101 applied mathematics, Set (abstract data type), Computational Mathematics, Convergence (routing), Computer Science::Mathematical Software, 0101 mathematics, ComputingMilieux_MISCELLANEOUS, Mathematics
Abstract: In many situations, it has been observed that significant convergence improvements can be achieved in preconditioned Krylov subspace methods by enriching them with some spectral information. On the other hand, effective preconditioning strategies are often designed where the preconditioner varies from one step to the next so that a flexible Krylov solver is required. In this paper, we present a new numerical technique for nonsymmetric problems that combines these two features. We illustrate the numerical behavior of the new solver both on a set of small academic test examples as well as on large industrial simulation arising in wave propagation simulations.
Published: 2010

310. Analysis of the solution phase of a parallel multifrontal approach

Author: Iain S. Duff, Patrick R. Amestoy, Tz. Slavova, Abdou Guermouche, Ecole Nationale Supérieure d'Electrotechnique, d'Electronique, d'Informatique, d'Hydraulique et de Télécommunications (ENSEEIHT), Institut National Polytechnique (Toulouse) (Toulouse INP), Université Fédérale Toulouse Midi-Pyrénées-Université Fédérale Toulouse Midi-Pyrénées, Centre Européen de Recherche et de Formation Avancée en Calcul Scientifique (CERFACS), CERFACS, Numerical Analysis Group - STFC Rutherford Appleton Laboratory, STFC Rutherford Appleton Laboratory (RAL), Science and Technology Facilities Council (STFC)-Science and Technology Facilities Council (STFC), and ANR-06-CIS6-0010,SOLSTICE,SOLveurs et SimulaTIons en Calculs Extrême(2006)
Subjects: Computer Networks and Communications, Computer science, Substitution (logic), MathematicsofComputing_NUMERICALANALYSIS, 010103 numerical & computational mathematics, Sparse approximation, Parallel computing, Solver, 01 natural sciences, Computer Graphics and Computer-Aided Design, Bottleneck, Theoretical Computer Science, 010101 applied mathematics, Factorization, Artificial Intelligence, Hardware and Architecture, Code (cryptography), Out-of-core algorithm, [INFO.INFO-DC]Computer Science [cs]/Distributed, Parallel, and Cluster Computing [cs.DC], 0101 mathematics, Massively parallel, Software
Abstract: International audience; We study the forward and backward substitution phases of a sparse multifrontal factorization. These phases are often neglected in papers on sparse direct factorization but, in many applications, they can be the bottleneck so it is crucial to implement them efficiently. In this work, we assume that the factors have been written on disk during the factorization phase, and we discuss the design of an efficient solution phase. We will look at the issues involved when we are solving the sparse systems on parallel computers and will consider in particular their solution in a limited memory environment when out-of-core working is required. Two different approaches are presented to read data from the disk, with a discussion on the advantages and the drawbacks of each. We present some experiments on realistic test problems using an out-of-core version of a sparse multifrontal code called MUMPS (MUltifrontal Massively Parallel Solver).
Published: 2010

311. Comparison of Direct and Indirect Combustion Noise Mechanisms in a Model Combustor

Author: Matthieu Leyko, Thierry Poinsot, Franck Nicoud, SNECMA Villaroche [Moissy-Cramayel], Safran Group, Centre Européen de Recherche et de Formation Avancée en Calcul Scientifique (CERFACS), CERFACS, Institut de Mathématiques et de Modélisation de Montpellier (I3M), Centre National de la Recherche Scientifique (CNRS)-Université Montpellier 2 - Sciences et Techniques (UM2)-Université de Montpellier (UM), Institut de mécanique des fluides de Toulouse (IMFT), Université Toulouse III - Paul Sabatier (UT3), Université Fédérale Toulouse Midi-Pyrénées-Université Fédérale Toulouse Midi-Pyrénées-Centre National de la Recherche Scientifique (CNRS)-Institut National Polytechnique (Toulouse) (Toulouse INP), and Université Fédérale Toulouse Midi-Pyrénées
Subjects: Overall pressure ratio, Engineering, 020209 energy, Acoustics, Nozzle, Aerospace Engineering, 02 engineering and technology, Combustion, 01 natural sciences, Physics::Fluid Dynamics, symbols.namesake, 0103 physical sciences, 0202 electrical engineering, electronic engineering, information engineering, Physics::Chemical Physics, 010301 acoustics, [SPI.ACOU]Engineering Sciences [physics]/Acoustics [physics.class-ph], business.industry, [SPI.FLUID]Engineering Sciences [physics]/Reactive fluid environment, Turbojet, Acoustic wave, [PHYS.MECA.ACOU]Physics [physics]/Mechanics [physics]/Acoustics [physics.class-ph], Mach number, Combustor, symbols, Combustion chamber, business
Abstract: International audience; Core noise in aeroengines is due to two main mechanisms: direct combustion noise, which is generated by the unsteady expansion of burning gases, and indirect combustion noise, which is due to the acceleration of entropy waves (temperature fluctuations generated by unsteady combustion) within the turbine stages. This paper shows how a simple burner model (a flame in a combustion chamber terminated by a nozzle) can be used to scale direct and indirect noise. An analytical formulation is used for waves generated by combustion. The transmission and generation of waves through the nozzle is calculated using both the analytical results of Marble and Candel (Marble, F. E., and Candel, S., "Acoustic Disturbances from Gas Nonuniformities Convected Through a Nozzle," Journal of Sound and Vibration, Vol. 55, 1977, pp. 225-243.) and a numerical tool. Numerical results for the nozzle verify and extend the analytical approach. The analytical relations for the combustion and the nozzle provide simple scaling laws for direct and indirect noise ratio as a function of the Mach number in the combustion chamber and at the nozzle outlet.
Published: 2009

312. Glacial climate sensitivity to different states of the Atlantic Meridional Overturning Circulation: results from the IPSL model

Author: Olivier Marti, Masa Kageyama, Ramdane Alkama, C. Marzin, Juliette Mignot, Didier Swingedouw, Modélisation du climat (CLIM), Laboratoire des Sciences du Climat et de l'Environnement [Gif-sur-Yvette] (LSCE), Université de Versailles Saint-Quentin-en-Yvelines (UVSQ)-Commissariat à l'énergie atomique et aux énergies alternatives (CEA)-Institut national des sciences de l'Univers (INSU - CNRS)-Université Paris-Saclay-Centre National de la Recherche Scientifique (CNRS)-Université de Versailles Saint-Quentin-en-Yvelines (UVSQ)-Commissariat à l'énergie atomique et aux énergies alternatives (CEA)-Institut national des sciences de l'Univers (INSU - CNRS)-Université Paris-Saclay-Centre National de la Recherche Scientifique (CNRS), Laboratoire d'Océanographie et du Climat : Expérimentations et Approches Numériques (LOCEAN), Muséum national d'Histoire naturelle (MNHN)-Institut de Recherche pour le Développement (IRD)-Université Pierre et Marie Curie - Paris 6 (UPMC)-Institut national des sciences de l'Univers (INSU - CNRS)-Centre National de la Recherche Scientifique (CNRS)-Institut Pierre-Simon-Laplace (IPSL (FR_636)), École normale supérieure - Paris (ENS-PSL), Université Paris sciences et lettres (PSL)-Université Paris sciences et lettres (PSL)-Université de Versailles Saint-Quentin-en-Yvelines (UVSQ)-Commissariat à l'énergie atomique et aux énergies alternatives (CEA)-Institut national des sciences de l'Univers (INSU - CNRS)-Université Paris Diderot - Paris 7 (UPD7)-École polytechnique (X)-Centre National d'Études Spatiales [Toulouse] (CNES)-Sorbonne Université (SU)-Centre National de la Recherche Scientifique (CNRS)-École normale supérieure - Paris (ENS-PSL), Université Paris sciences et lettres (PSL)-Université Paris sciences et lettres (PSL)-Université de Versailles Saint-Quentin-en-Yvelines (UVSQ)-Commissariat à l'énergie atomique et aux énergies alternatives (CEA)-Université Paris Diderot - Paris 7 (UPD7)-École polytechnique (X)-Centre National d'Études Spatiales [Toulouse] (CNES)-Sorbonne Université (SU)-Centre National de la Recherche Scientifique (CNRS), Centre Européen de Recherche et de Formation Avancée en Calcul Scientifique (CERFACS), Université de Versailles Saint-Quentin-en-Yvelines (UVSQ)-Commissariat à l'énergie atomique et aux énergies alternatives (CEA)-Institut national des sciences de l'Univers (INSU - CNRS)-Université Paris-Saclay-Centre National de la Recherche Scientifique (CNRS), Centre national de recherches météorologiques (CNRM), Institut national des sciences de l'Univers (INSU - CNRS)-Observatoire Midi-Pyrénées (OMP), Institut de Recherche pour le Développement (IRD)-Université Toulouse III - Paul Sabatier (UT3), Université de Toulouse (UT)-Université de Toulouse (UT)-Institut national des sciences de l'Univers (INSU - CNRS)-Centre National d'Études Spatiales [Toulouse] (CNES)-Centre National de la Recherche Scientifique (CNRS)-Météo-France -Institut de Recherche pour le Développement (IRD)-Université Toulouse III - Paul Sabatier (UT3), Université de Toulouse (UT)-Université de Toulouse (UT)-Institut national des sciences de l'Univers (INSU - CNRS)-Centre National d'Études Spatiales [Toulouse] (CNES)-Centre National de la Recherche Scientifique (CNRS)-Météo-France -Centre National de la Recherche Scientifique (CNRS), Modelling the Earth Response to Multiple Anthropogenic Interactions and Dynamics (MERMAID), Institut national des sciences de l'Univers (INSU - CNRS)-Université Paris-Saclay-Centre National de la Recherche Scientifique (CNRS)-Commissariat à l'énergie atomique et aux énergies alternatives (CEA)-Université de Versailles Saint-Quentin-en-Yvelines (UVSQ)-Institut national des sciences de l'Univers (INSU - CNRS)-Université Paris-Saclay-Centre National de la Recherche Scientifique (CNRS)-Commissariat à l'énergie atomique et aux énergies alternatives (CEA)-Université de Versailles Saint-Quentin-en-Yvelines (UVSQ), Institut de Recherche pour le Développement (IRD)-Centre National de la Recherche Scientifique (CNRS)-Institut national des sciences de l'Univers (INSU - CNRS)-Université Pierre et Marie Curie - Paris 6 (UPMC)-Muséum national d'Histoire naturelle (MNHN)-Institut Pierre-Simon-Laplace (IPSL (FR_636)), École normale supérieure - Paris (ENS Paris), Université Paris sciences et lettres (PSL)-Université Paris sciences et lettres (PSL)-Université de Versailles Saint-Quentin-en-Yvelines (UVSQ)-Commissariat à l'énergie atomique et aux énergies alternatives (CEA)-Institut national des sciences de l'Univers (INSU - CNRS)-Université Paris Diderot - Paris 7 (UPD7)-École polytechnique (X)-Centre National d'Études Spatiales [Toulouse] (CNES)-Sorbonne Université (SU)-Centre National de la Recherche Scientifique (CNRS)-École normale supérieure - Paris (ENS Paris), CERFACS, Institut national des sciences de l'Univers (INSU - CNRS)-Université Paris-Saclay-Centre National de la Recherche Scientifique (CNRS)-Commissariat à l'énergie atomique et aux énergies alternatives (CEA)-Université de Versailles Saint-Quentin-en-Yvelines (UVSQ), and Institut national des sciences de l'Univers (INSU - CNRS)-Météo France-Centre National de la Recherche Scientifique (CNRS)
Subjects: 010506 paleontology, 010504 meteorology & atmospheric sciences, Atmospheric circulation, lcsh:Environmental protection, Stratigraphy, Tropical Atlantic, 010502 geochemistry & geophysics, 01 natural sciences, Atlantic Equatorial mode, lcsh:Environmental pollution, Atlantic multidecadal oscillation, lcsh:TD169-171.8, [SDU.ENVI]Sciences of the Universe [physics]/Continental interfaces, environment, lcsh:Environmental sciences, 0105 earth and related environmental sciences, lcsh:GE1-350, [SDU.OCEAN]Sciences of the Universe [physics]/Ocean, Atmosphere, Global and Planetary Change, North Atlantic Deep Water, Paleontology, Gulf Stream, Oceanography, Shutdown of thermohaline circulation, 13. Climate action, Climatology, lcsh:TD172-193.5, Thermohaline circulation, Geology
Abstract: Numerous records from the North Atlantic and the surrounding continents have shown rapid and large amplitude climate variability during the last glacial period. This variability has often been associated to changes in the Atlantic Meridional Overturning Circulation (AMOC). Rapid climate change on the same time scales has also been reconstructed for sites far away from the North Atlantic, such as the tropical Atlantic, the East Pacific and Asia. The mechanisms explaining these climatic responses to the state of the AMOC are far from being completely understood, especially in a glacial context. Here we study three glacial simulations characterised by different AMOC strengths: 18, 15 and 2 Sv. With these simulations, we analyse the global climate sensitivity to a weak (18 to 15 Sv) and a strong (15 to 2 Sv) decrease in the AMOC strength. A weak decrease in the AMOC is associated, in our model simulations, to the classical North Atlantic and European cooling, but this cooling is not homogeneous over this region. We investigate the reasons for a lesser cooling (or even slight warming in some cases) over the Norwegian Sea and Northwestern Europe. It appears that the convection site in this area is active in both simulations, but that convection is unexpectedly stronger in the 15 Sv simulation. Due to the large variability of the atmosphere, it is difficult to definitely establish what is the origin of this climatic difference, but it appears that the atmospheric circulation anomaly helps sustaining the activity of this convection sites. Far from the North Atlantic, the climatic response is of small amplitude, the only significant change appearing in summer over the tropical Atlantic, where the Inter-Tropical Convergence Zone (ITCZ) shifts southward. The climate differences between the 15 Sv and 2 Sv simulations are much larger and our analyses focus on three areas: the North Atlantic and surrounding regions, the Tropics and the Indian monsoon region. We study the timing of appearance of these responses to the AMOC shutdown, which gives some clues about the mechanisms for these teleconnections. We show that the North Atlantic cooling associated with the collapse of the AMOC induces a cyclonic atmospheric circulation anomaly centered over the North Atlantic, which modulates the eastward advection of the cold anomaly over the Eurasian continent. It can explain that the cooling is not as strong over Western Europe as over the North Atlantic and the rest of the Eurasian continent. Another modification in the northern extratropical stationary waves occurs over the Eastern Pacific, explaining a warming over Northwestern America. In the Tropics, the ITCZ southward shift in this simulation appears to be strongest over the Atlantic and Eastern Pacific and results from an ajustment of the atmospheric and oceanic transports. Finally, the Indian monsoon weakening also appears to be connected to the tropospheric cooling over Eurasia.
Published: 2009

313. Ocean Data Assimilation Systems for GODAE

Author: Kristian Mogensen, Charles-Emmanuel Testut, Pierre Brasseur, Peter R. Oke, Jacques Verron, Anthony T. Weaver, Jeannie Telisha Cummings, Ichiro Fukumori, Matthew Martin, Laurent Bertino, Masafumi Kamachi, Nansen Environmental and Remote Sensing Center [Bergen] (NERSC), Laboratoire des Écoulements Géophysiques et Industriels [Grenoble] (LEGI), Institut polytechnique de Grenoble - Grenoble Institute of Technology (Grenoble INP )-Centre National de la Recherche Scientifique (CNRS)-Université Joseph Fourier - Grenoble 1 (UJF), California Institute of Technology (CALTECH), Japan Agency for Marine-Earth Science and Technology (JAMSTEC), Meteorological Office, European Centre for Medium-Range Weather Forecasts (ECMWF), Centre Européen de Recherche et de Formation Avancée en Calcul Scientifique (CERFACS), and CERFACS
Subjects: Meteorological reanalysis, 010504 meteorology & atmospheric sciences, Meteorology, Forecast error, 010505 oceanography, Weather forecasting, Assimilation (biology), ocean data assimilation, Covariance, GODAE, Oceanography, computer.software_genre, 01 natural sciences, Performance results, lcsh:Oceanography, Data assimilation, Geography, Climatology, lcsh:GC1-1581, Matematikk og Naturvitenskap: 400 [VDP], 14. Life underwater, computer, [SDU.STU.OC]Sciences of the Universe [physics]/Earth Sciences/Oceanography, 0105 earth and related environmental sciences
Abstract: International audience; Ocean data assimilation has reached a sufficient level of maturity such that observations are routinely combined with model forecasts to produce a variety of ocean products. Approaches to ocean data assimilation vary widely both in terms of the sophistication of the method and the observations assimilated, and also in terms of specification of the forecast error covariances, model biases, observation errors, and quality-control procedures. In this paper, we describe some of the ocean data assimilation systems that have been developed within the Global Ocean Data Assimilation Experiment (GODAE) community. We discuss assimilation methods, observations assimilated, and techniques used to specify error covariances. In addition, we describe practical implementation aspects and present analysis performance results for some of the analysis systems. Finally, we describe plans for improving the assimilation systems in the post-GODAE time period beyond 2008.
Published: 2009

314. Two-dimensional reconstruction of past sea level (1950–2003) from tide gauge data and an Ocean General Circulation Model

Author: Anny Cazenave, P. Rogel, A. Lombard, W. Llovel, M. B. Nguyen, GOHS, Laboratoire d'études en Géophysique et océanographie spatiales (LEGOS), Institut de Recherche pour le Développement (IRD)-Université Toulouse III - Paul Sabatier (UT3), Université de Toulouse (UT)-Université de Toulouse (UT)-Institut national des sciences de l'Univers (INSU - CNRS)-Observatoire Midi-Pyrénées (OMP), Université de Toulouse (UT)-Université de Toulouse (UT)-Institut national des sciences de l'Univers (INSU - CNRS)-Centre National d'Études Spatiales [Toulouse] (CNES)-Centre National de la Recherche Scientifique (CNRS)-Météo-France -Institut de Recherche pour le Développement (IRD)-Institut national des sciences de l'Univers (INSU - CNRS)-Centre National d'Études Spatiales [Toulouse] (CNES)-Centre National de la Recherche Scientifique (CNRS)-Météo-France -Centre National de la Recherche Scientifique (CNRS)-Institut de Recherche pour le Développement (IRD)-Université Toulouse III - Paul Sabatier (UT3), Université de Toulouse (UT)-Université de Toulouse (UT)-Institut national des sciences de l'Univers (INSU - CNRS)-Centre National d'Études Spatiales [Toulouse] (CNES)-Centre National de la Recherche Scientifique (CNRS)-Météo-France -Institut de Recherche pour le Développement (IRD)-Institut national des sciences de l'Univers (INSU - CNRS)-Centre National d'Études Spatiales [Toulouse] (CNES)-Centre National de la Recherche Scientifique (CNRS)-Météo-France -Centre National de la Recherche Scientifique (CNRS), Centre Européen de Recherche et de Formation Avancée en Calcul Scientifique (CERFACS), Centre National d'Études Spatiales [Toulouse] (CNES), Echanges Côte-Large (ECOLA), Université Fédérale Toulouse Midi-Pyrénées-Université Fédérale Toulouse Midi-Pyrénées-Institut national des sciences de l'Univers (INSU - CNRS)-Observatoire Midi-Pyrénées (OMP), Météo France-Centre National d'Études Spatiales [Toulouse] (CNES)-Université Fédérale Toulouse Midi-Pyrénées-Centre National de la Recherche Scientifique (CNRS)-Institut de Recherche pour le Développement (IRD)-Météo France-Centre National d'Études Spatiales [Toulouse] (CNES)-Centre National de la Recherche Scientifique (CNRS)-Institut de Recherche pour le Développement (IRD)-Centre National de la Recherche Scientifique (CNRS)-Institut de Recherche pour le Développement (IRD)-Université Toulouse III - Paul Sabatier (UT3), Météo France-Centre National d'Études Spatiales [Toulouse] (CNES)-Université Fédérale Toulouse Midi-Pyrénées-Centre National de la Recherche Scientifique (CNRS)-Institut de Recherche pour le Développement (IRD)-Météo France-Centre National d'Études Spatiales [Toulouse] (CNES)-Centre National de la Recherche Scientifique (CNRS)-Institut de Recherche pour le Développement (IRD)-Centre National de la Recherche Scientifique (CNRS), CERFACS [Toulouse], and Institut national des sciences de l'Univers (INSU - CNRS)-Centre National de la Recherche Scientifique (CNRS)
Subjects: 010504 meteorology & atmospheric sciences, EMPIRICAL ORTHOGONAL FUNCTIONS, Stratigraphy, lcsh:Environmental protection, Empirical orthogonal functions, 02 engineering and technology, 01 natural sciences, REANALYSIS, DATA ASSIMILATION, Data assimilation, lcsh:Environmental pollution, 0202 electrical engineering, electronic engineering, information engineering, lcsh:TD169-171.8, 14. Life underwater, Altimeter, ALTIMETRY, SATELLITE, Sea level, lcsh:Environmental sciences, 0105 earth and related environmental sciences, [SDU.OCEAN]Sciences of the Universe [physics]/Ocean, Atmosphere, lcsh:GE1-350, Global and Planetary Change, Past sea level, ICE, Paleontology, 020206 networking & telecommunications, RISE, Ocean general circulation model, 6. Clean water, 13. Climate action, Climatology, lcsh:TD172-193.5, SURFACE TEMPERATURE, Tide gauge, Satellite, Geology
Abstract: ISI Document Delivery No.: 464XM Times Cited: 19 Cited Reference Count: 32 Cited References: Alvera-Azcarate A, 2005, OCEAN MODEL, V9, P325, DOI 10.1016/j.ocemod.2004.08.001 Berge-Nguyen M, 2008, GLOBAL PLANET CHANGE, V62, P1, DOI 10.1016/j.gloplacha.2007.11.007 Bindoff NL, 2007, CLIMATE CHANGE 2007: THE PHYSICAL SCIENCE BASIS, P385 Cabanes C, 2001, SCIENCE, V294, P840, DOI 10.1126/science.1063556 CAZENAVE A, 2004, REV GEOPHYS, V42, DOI DOI 10.1029/2003RG000139 Chambers DP, 2002, PHYS CHEM EARTH, V27, P1407, DOI 10.1016/S1474-7065(02)00078-5 Church JA, 2004, J CLIMATE, V17, P2609, DOI 10.1175/1520-0442(2004)0172.0.CO;2 Church JA, 2006, GLOBAL PLANET CHANGE, V53, P155, DOI 10.1016/j.gloplacha.2006.04.001 Daget N, 2009, Q J ROY METEOR SOC, V135, P1071, DOI 10.1002/qj.412 Holgate SJ, 2007, GEOPHYS RES LETT, V34, DOI 10.1029/2006GL028492 Holgate SJ, 2004, GEOPHYS RES LETT, V31, DOI 10.1029/2004GL019626 INGLEBY B, 2007, J MARINE SYST, V65, P148 Kalnay E, 1996, B AM METEOROL SOC, V77, P437, DOI 10.1175/1520-0477(1996)0772.0.CO;2 Kaplan A, 1998, J GEOPHYS RES-OCEANS, V103, P18567, DOI 10.1029/97JC01736 Kuo CY, 2008, TERR ATMOS OCEAN SCI, V19, P21, DOI 10.3319/TAO.2008.19.1-2.21(SA) LEVITUS S, 1994, WORLD OCEAN ATLAS NA, V4 LEVITUS S, 1994, WORLD OCEAN ATLAS NA, V3 Lombard A, 2005, GLOBAL PLANET CHANGE, V47, P1, DOI 10.1016/j.gloplacha.2004.11.016 Madec G., 1998, OPA 8 1 OCEAN GEN CI Meehl GA, 2007, CLIMATE CHANGE 2007: THE PHYSICAL SCIENCE BASIS, P747 Peltier WR, 2004, ANNU REV EARTH PL SC, V32, P111, DOI 10.1146/annurev.earth.32.082503.144359 Preisendorfer R.W., 1988, DEV ATMOSPHERIC SCI, V17 Rayner NA, 2003, J GEOPHYS RES-ATMOS, V108, DOI 10.1029/2002JD002670 Ricci S, 2005, MON WEATHER REV, V133, P317, DOI 10.1175/MWR2872.1 Roullet G, 2000, J GEOPHYS RES-OCEANS, V105, P23927, DOI 10.1029/2000JC900089 SMITH TM, 1994, J CLIMATE, V7, P949, DOI 10.1175/1520-0442(1994)0072.0.CO;2 Smith TM, 1996, J CLIMATE, V9, P1403, DOI 10.1175/1520-0442(1996)0092.0.CO;2 Toumazou V, 2001, MON WEATHER REV, V129, P1243, DOI 10.1175/1520-0493(2001)1292.0.CO;2 Troccoli A, 2004, ERA 40 PROJECT REPOR, V13 Uppala SM, 2005, Q J ROY METEOR SOC, V131, P2961, DOI 10.1256/qj.04.176 Weaver AT, 2005, Q J ROY METEOR SOC, V131, P3605, DOI 10.1256/qj.05.119 Woodworth PL, 2003, J COASTAL RES, V19, P287 Llovel, W. Cazenave, A. Rogel, P. Lombard, A. Nguyen, M. B. 19 COPERNICUS GESELLSCHAFT MBH GOTTINGEN CLIM PAST; A two-dimensional reconstruction of past sea level is proposed at yearly interval over the period 1950-2003 using tide gauge records from 99 selected sites and 44-year long (1960-2003) 2 degrees x2 degrees sea level grids from the OPA/NEMO ocean general circulation model with data assimilation. We focus on the regional variability and do not attempt to compute the global mean trend. An Empirical Orthogonal Function decomposition of the reconstructed sea level grids over 1950-2003 displays leading modes that reflect two main components: (1) a long-term (multi-decadal), regionally variable signal and (2) an interannual, regionally variable signal dominated by the signature of El Nino-Southern Oscillation. Tests show that spatial trend patterns of the 54-year long reconstructed sea level significantly depend on the temporal length of the two-dimensional sea level signal used for the reconstruction (i.e., the length of the gridded OPA/NEMO sea level time series). On the other hand, interannual variability is well reconstructed, even when only similar to 10-years of model grids are used. The robustness of the results is assessed, leaving out successively each of the 99 tide gauges used for the reconstruction and comparing observed and reconstructed time series at the non considered tide gauge site. The reconstruction performs well at most tide gauges, especially at interannual frequency.
Published: 2009

315. Effect of multiperforated plates on the acoustic modes in combustors

Author: Claude Sensiau, Simon Mendez, Franck Nicoud, Thierry Poinsot, Elsa Gullaud, Centre Européen de Recherche et de Formation Avancée en Calcul Scientifique (CERFACS), CERFACS, SNECMA Villaroche [Moissy-Cramayel], Safran Group, Institut de Mathématiques et de Modélisation de Montpellier (I3M), Centre National de la Recherche Scientifique (CNRS)-Université Montpellier 2 - Sciences et Techniques (UM2)-Université de Montpellier (UM), Institut de mécanique des fluides de Toulouse (IMFT), Université Toulouse III - Paul Sabatier (UT3), Université Fédérale Toulouse Midi-Pyrénées-Université Fédérale Toulouse Midi-Pyrénées-Centre National de la Recherche Scientifique (CNRS)-Institut National Polytechnique (Toulouse) (Toulouse INP), and Université Fédérale Toulouse Midi-Pyrénées
Subjects: Absorption (acoustics), Engineering, Helmholtz equation, Physics::Instrumentation and Detectors, BIAS FLOW, 020209 energy, Strategy and Management, Acoustics, Combustion, 02 engineering and technology, Damping, 01 natural sciences, IMPEDANCE, 010305 fluids & plasmas, symbols.namesake, 0103 physical sciences, 0202 electrical engineering, electronic engineering, information engineering, Media Technology, General Materials Science, Sensitivity (control systems), Combustion instabilities, [SPI.ACOU]Engineering Sciences [physics]/Acoustics [physics.class-ph], Marketing, Multiperforated plates, LARGE-EDDY SIMULATION, business.industry, [SPI.FLUID]Engineering Sciences [physics]/Reactive fluid environment, PERFORATED PLATES, Solver, [PHYS.MECA.ACOU]Physics [physics]/Mechanics [physics]/Acoustics [physics.class-ph], Flow velocity, Helmholtz free energy, symbols, Combustion chamber, business, Large eddy simulation
Abstract: International audience; The analytical model derived by Howe assessing the acoustic effect of perforated plates has been implemented in a 3D Helmholtz solver. This solver allows one to compute the acoustic modes of industrial chambers taking into account the multiperforated plates present for the cooling of the walls. An academic test case consisting of two coaxial cylinders, with the inner one being perforated is used to validate the implementation in the general purpose AVSP code. This case is also used to show the effects of the presence of the plates. In particular, the sensitivity of the acoustic damping to the bias flow speed will be studied. A maximum absorption speed is shown, and the behaviour towards an infinite speed will be illustrated by the academic case. Computations are also conducted in the case of an industrial helicopter chamber. The value of the maximum absorption speed is discussed to explain why the modes are in fact not much absorbed by the perforated plates, and that the frequencies are the same as for walls.
Published: 2009

316. On the Arithmetic Intensity of Distributed-Memory Dense Matrix Multiplication Involving a Symmetric Input Matrix (SYMM)

Author: Agullo, Emmanuel, Buttari, Alfredo, Coulaud, Olivier, Eyraud-Dubois, Lionel, Faverge, Mathieu, Franc, Alain, Guermouche, Abdou, Jego, Antoine, Peressoni, Romain, Pruvost, Florent, COmposabilité Numerique and parallèle pour le CAlcul haute performanCE (CONCACE), Centre Européen de Recherche et de Formation Avancée en Calcul Scientifique (CERFACS)-Airbus [France]-Inria Bordeaux - Sud-Ouest, Institut National de Recherche en Informatique et en Automatique (Inria)-Institut National de Recherche en Informatique et en Automatique (Inria), Algorithmes Parallèles et Optimisation (IRIT-APO), Institut de recherche en informatique de Toulouse (IRIT), Université Toulouse Capitole (UT Capitole), Université de Toulouse (UT)-Université de Toulouse (UT)-Université Toulouse - Jean Jaurès (UT2J), Université de Toulouse (UT)-Université Toulouse III - Paul Sabatier (UT3), Université de Toulouse (UT)-Centre National de la Recherche Scientifique (CNRS)-Institut National Polytechnique (Toulouse) (Toulouse INP), Université de Toulouse (UT)-Toulouse Mind & Brain Institut (TMBI), Université Toulouse - Jean Jaurès (UT2J), Université de Toulouse (UT)-Université de Toulouse (UT)-Université Toulouse III - Paul Sabatier (UT3), Université de Toulouse (UT)-Université Toulouse Capitole (UT Capitole), Université de Toulouse (UT), Centre National de la Recherche Scientifique (CNRS), Laboratoire Bordelais de Recherche en Informatique (LaBRI), Université de Bordeaux (UB)-École Nationale Supérieure d'Électronique, Informatique et Radiocommunications de Bordeaux (ENSEIRB)-Centre National de la Recherche Scientifique (CNRS), Outils et Optimisations pour le Calcul Haute Performance et l'Apprentissage (TOPAL), Université de Bordeaux (UB)-École Nationale Supérieure d'Électronique, Informatique et Radiocommunications de Bordeaux (ENSEIRB)-Centre National de la Recherche Scientifique (CNRS)-Université de Bordeaux (UB)-École Nationale Supérieure d'Électronique, Informatique et Radiocommunications de Bordeaux (ENSEIRB)-Centre National de la Recherche Scientifique (CNRS)-Inria Bordeaux - Sud-Ouest, Institut National de Recherche en Informatique et en Automatique (Inria)-Institut National de Recherche en Informatique et en Automatique (Inria)-Institut Polytechnique de Bordeaux (Bordeaux INP), Biodiversité, Gènes & Communautés (BioGeCo), Université de Bordeaux (UB)-Institut National de Recherche pour l’Agriculture, l’Alimentation et l’Environnement (INRAE), from patterns to models in computational biodiversity and biotechnology (PLEIADE), Institut National de Recherche en Informatique et en Automatique (Inria)-Institut National de Recherche en Informatique et en Automatique (Inria)-Biodiversité, Gènes & Communautés (BioGeCo), Université de Bordeaux (UB)-Institut National de Recherche pour l’Agriculture, l’Alimentation et l’Environnement (INRAE)-Institut National de Recherche pour l’Agriculture, l’Alimentation et l’Environnement (INRAE), Service Expérimentation et Développement [Bordeaux] (SED), Inria Bordeaux - Sud-Ouest, Région Nouvelle-Aquitaine (2018-1R50119 HPC scalable ecosystem), IEEE, and ANR-19-CE46-0009,SOLHARIS,Solveurs pour architectures hétérogènes utilisant des supports d'exécution, objectif scalabilité(2019)
Subjects: Matrix multiplication, Symmetric, GEMM, 2DBC, SYMM, task-based programming, TBC, [INFO.INFO-DC]Computer Science [cs]/Distributed, Parallel, and Cluster Computing [cs.DC], [INFO.INFO-BI]Computer Science [cs]/Bioinformatics [q-bio.QM], 2.5D, SBC, 3D
Abstract: International audience; Dense matrix multiplication involving a symmetric input matrix (SYMM) is implemented in reference distributed-memory codes with the same data distribution as its general analogue (GEMM). We show that, when the symmetric matrix is dominant, such a 2D block-cyclic (2D BC) scheme leads to a lower arithmetic intensity (AI) of SYMM than that of GEMM by a factor of 2. We propose alternative data distributions preserving the memory benefit of SYMM of storing only half of the matrix while achieving up to the same AI as GEMM. We also show that, in the case we can afford the same memory footprint as GEMM, SYMM can achieve a higher AI. We propose a task-based design of SYMM independent of the data distribution. This design allows for scalable A-stationary SYMM with which all discussed data distributions, may they be very irregular, can be easily assessed. We have integrated the resulting code in a reduction dimension algorithm involving a randomized singular value decomposition dominated by SYMM. An experimental study shows a compelling impact on performance.
Published: 2023

317. Development and validation of Navier–Stokes characteristic boundary conditions applied to turbomachinery simulations using the lattice Boltzmann method

Author: Thomas Gianoli, Jean‐François Boussuge, Pierre Sagaut, Jérôme de Laborderie, Laboratoire de Mécanique, Modélisation et Procédés Propres (M2P2), Aix Marseille Université (AMU)-École Centrale de Marseille (ECM)-Centre National de la Recherche Scientifique (CNRS), Centre Européen de Recherche et de Formation Avancée en Calcul Scientifique (CERFACS), and Safran Aircraft Engines
Subjects: Mechanics of Materials, lattice Boltzmann method, LODI, Applied Mathematics, Mechanical Engineering, Computational Mechanics, characteristic boundary conditions, turbomachinery, Computer Science Applications, [SPI.MECA.MEFL]Engineering Sciences [physics]/Mechanics [physics.med-ph]/Fluids mechanics [physics.class-ph]
Abstract: International audience; This article reports a procedure to implement as well as to validate non-reflecting boundary conditions applied for turbomachinery simulations, using Navier-Stokes characteristic boundary conditions in a compressible lattice Boltzmann solver. The implementation of both an inlet condition imposing total pressure, total temperature, and flow angles, as well as an outlet condition imposing a static pressure profile that allows the simulation to reach a simplified radial equilibrium, is described within the context of a lattice Boltzmann approach. The treatment at the boundaries relies on the characteristic methodology to derive conditions which are non-reflecting in terms of acoustics and is also compatible with turbulence injection at the inlet. These properties are evaluated on test cases of increasing complexity, ranging from a simple 2D periodic domain to an S-duct stage with turbulence injection.
Published: 2023

318. Estimation of the local diffusion tensor and normalization for heterogeneous correlation modelling using a diffusion equation

Author: Sebastien Massart, Olivier Pannekoucke, Centre national de recherches météorologiques (CNRM), Institut national des sciences de l'Univers (INSU - CNRS)-Observatoire Midi-Pyrénées (OMP), Institut de Recherche pour le Développement (IRD)-Université Toulouse III - Paul Sabatier (UT3), Université de Toulouse (UT)-Université de Toulouse (UT)-Institut national des sciences de l'Univers (INSU - CNRS)-Centre National d'Études Spatiales [Toulouse] (CNES)-Centre National de la Recherche Scientifique (CNRS)-Météo-France -Institut de Recherche pour le Développement (IRD)-Université Toulouse III - Paul Sabatier (UT3), Université de Toulouse (UT)-Université de Toulouse (UT)-Institut national des sciences de l'Univers (INSU - CNRS)-Centre National d'Études Spatiales [Toulouse] (CNES)-Centre National de la Recherche Scientifique (CNRS)-Météo-France -Centre National de la Recherche Scientifique (CNRS), Centre Européen de Recherche et de Formation Avancée en Calcul Scientifique (CERFACS), Groupe d'étude de l'atmosphère météorologique (CNRM-GAME), Institut national des sciences de l'Univers (INSU - CNRS)-Météo France-Centre National de la Recherche Scientifique (CNRS), and CERFACS
Subjects: [SDU.OCEAN]Sciences of the Universe [physics]/Ocean, Atmosphere, Normalization (statistics), Atmospheric Science, assimilation, Diffusion equation, 010504 meteorology & atmospheric sciences, Covariance matrix, ensemble, 0207 environmental engineering, 02 engineering and technology, 01 natural sciences, Correlation function (statistical mechanics), Matrix (mathematics), Error function, Calculus, Statistical physics, diffusion operator, 020701 environmental engineering, Anisotropy, background-error correlation modelling, 0105 earth and related environmental sciences, Mathematics, Diffusion MRI
Abstract: As the background error covariance matrix is a key component of any assimilation system, its modelling is an important step. Usually, this matrix is decomposed into correlations and variance matrices. An interesting method for modelling the correlation matrix of the background error for complex geometry, like ocean grid, consists in computing correlation functions using a diffusion operator. The background error correlation functions can be estimated for example from an ensemble of perturbed forecasts. The diffusion operator is able to represent heterogeneous correlation functions at a reasonable numerical cost. But afirst challenge resides in the determination of the local diffusion tensor corresponding to the local correlation function. Then the second challenge resides in the determination of the normalization to make sure that the matrix modelled through the diffusion operator is a correlation matrix. In this article, we propose to build a background error correlation matrix using a diffusion operator based on a local diffusion tensor. The estimation of this local tensor is performed using an ensemble of perturbed forecasts. A validation within a randomization method illustrates the feasibility and the accuracy of the proposed method. In particular, it is shown that the local geographical variations of diagnosed correlation functions (through an ensemble of perturbed forecast) are well represented. This is first illustrated in an analytical one-dimensional framework. In that context, the diffusion field and the normalization field are deduced from a given correlation length-scale field. The resulting length-scales are shown to correspond to the initial length-scale when the given length-scale field spectrum is red. The approximate normalization, computed from the local length-scale, is close to the true normalization under the same condition of a red spectrum. Then, the method is illustrated in a real context using an ensemble of perturbed forecasts from the MOCAGE-PALM assimilation system. In that case, length-scale and anisotropy diagnosis reveal the complexity of the correlation of stratospheric ozone forecast errors. The local diffusion tensor deduced from these diagnosis are shown be able to represent such an existing heterogeneity and anisotropy. As in the one-dimensional case, the approximate normalization, based on the local diffusion tensor, appears to be a really good approximation of the true normalization.
Published: 2008

319. Ozone loss in the 2002–2003 Arctic vortex deduced from the assimilation of Odin/SMR O3 and N2O measurements: N2O as a dynamical tracer

Author: D. Cariolle, L. El Amraoui, F. Karcher, Sebastien Massart, Vincent-Henri Peuch, N. Semane, Philippe Ricaud, H. Teyssèdre, Groupe d'étude de l'atmosphère météorologique (CNRM-GAME), Institut national des sciences de l'Univers (INSU - CNRS)-Météo France-Centre National de la Recherche Scientifique (CNRS), Laboratoire d'aérologie (LAERO), Centre National de la Recherche Scientifique (CNRS)-Observatoire Midi-Pyrénées (OMP), Météo France-Centre National d'Études Spatiales [Toulouse] (CNES)-Université Fédérale Toulouse Midi-Pyrénées-Centre National de la Recherche Scientifique (CNRS)-Institut de Recherche pour le Développement (IRD)-Météo France-Centre National d'Études Spatiales [Toulouse] (CNES)-Université Fédérale Toulouse Midi-Pyrénées-Centre National de la Recherche Scientifique (CNRS)-Institut de Recherche pour le Développement (IRD)-Université Toulouse III - Paul Sabatier (UT3), Université Fédérale Toulouse Midi-Pyrénées, Centre Européen de Recherche et de Formation Avancée en Calcul Scientifique (CERFACS), CERFACS, Centre Nationale de Recherches Météorologiques, Centre national de recherches météorologiques (CNRM), Institut national des sciences de l'Univers (INSU - CNRS)-Observatoire Midi-Pyrénées (OMP), Institut de Recherche pour le Développement (IRD)-Université Toulouse III - Paul Sabatier (UT3), Université de Toulouse (UT)-Université de Toulouse (UT)-Institut national des sciences de l'Univers (INSU - CNRS)-Centre National d'Études Spatiales [Toulouse] (CNES)-Centre National de la Recherche Scientifique (CNRS)-Météo-France -Institut de Recherche pour le Développement (IRD)-Université Toulouse III - Paul Sabatier (UT3), Université de Toulouse (UT)-Université de Toulouse (UT)-Institut national des sciences de l'Univers (INSU - CNRS)-Centre National d'Études Spatiales [Toulouse] (CNES)-Centre National de la Recherche Scientifique (CNRS)-Météo-France -Centre National de la Recherche Scientifique (CNRS), Université Toulouse III - Paul Sabatier (UT3), Université de Toulouse (UT)-Université de Toulouse (UT)-Observatoire Midi-Pyrénées (OMP), and Université de Toulouse (UT)-Université de Toulouse (UT)-Institut national des sciences de l'Univers (INSU - CNRS)-Centre National d'Études Spatiales [Toulouse] (CNES)-Centre National de la Recherche Scientifique (CNRS)-Météo-France -Institut de Recherche pour le Développement (IRD)-Institut national des sciences de l'Univers (INSU - CNRS)-Centre National d'Études Spatiales [Toulouse] (CNES)-Centre National de la Recherche Scientifique (CNRS)-Météo-France -Centre National de la Recherche Scientifique (CNRS)
Subjects: chemical ozone loss, Perte d'ozone, Atmospheric Science, Ozone, 010504 meteorology & atmospheric sciences, Assimilation des données chimiques, [SDU.STU.ME]Sciences of the Universe [physics]/Earth Sciences/Meteorology, 010501 environmental sciences, Atmospheric sciences, 01 natural sciences, chemistry.chemical_compound, Polar vortex, Potential vorticity, Chemical data assimilation, Modèle de transport chimique, Stratosphere, 0105 earth and related environmental sciences, [PHYS.PHYS.PHYS-AO-PH]Physics [physics]/Physics [physics]/Atmospheric and Oceanic Physics [physics.ao-ph], Radiometer, Advection, Ozone depletion, diabatic descent, Vortex, chemistry, 13. Climate action, Climatology, Descente diabatique
Abstract: International audience; In this paper we investigate the evolution of the northern polar vortex during the winter 2002–2003 in the lower stratosphere by using assimilated fields of ozone (O3) and nitrous oxide (N2O). Both O3 and N2O used in this study are obtained from the Sub-Millimetre Radiometer (SMR) aboard the Odin satellite and are assimilated into the global three-dimensional chemistry transport model of M´et´eo-France, MOCAGE. O3 is assimilated into the ‘full' model including both advection and chemistry whereas N2O is only assimilated with advection since it is characterized by good chemical stability in the lower stratosphere. We show the ability of the assimilated N2O field to localize the edge of the polar vortex. The results are compared to the use of the maximum gradient of modified potential vorticity as a vortex edge criterion. The O3 assimilated field serves to evaluate the ozone evolution and to deduce the ozone depletion inside the vortex. The chemical ozone loss is estimated using the vortex-average technique. The N2O assimilated field is also used to substract out the effect of subsidence in order to extract the actual chemical ozone loss. Results show that the chemical ozone loss is 1.1 ± 0.3 ppmv on the 25 ppbv N2O level between mid-November and mid-January, and 0.9 ± 0.2 ppmv on the 50 ppbv N2O level between mid-November and the end of January. A linear fit over the same periods gives a chemical ozone loss rate of ∼18 ppbv day−1 and ∼9.3 ppbv day−1 on the 25 ppbv and 50 ppbv N2O levels, respectively. The vortex-averaged ozone loss profile from the O3 assimilated field shows a maximum of 0.98 ppmv at 475 K. Comparisons to other results reported by different authors using different techniques and different observations give satisfactory results.
Published: 2008

320. Partitioning Sparse Matrices for Parallel Preconditioned Iterative Methods

Author: Bora Uçar, Cevdet Aykanat, Centre Européen de Recherche et de Formation Avancée en Calcul Scientifique (CERFACS), CERFACS, Department of Computer Engineering (Bilkent-CS), Bilkent University [Ankara], Aykanat, Cevdet, and Roma, Equipe
Subjects: Parallel computing, Hypergraph, Matrix partitioning, Computer science, Iterative method, [INFO.INFO-DS]Computer Science [cs]/Data Structures and Algorithms [cs.DS], MathematicsofComputing_NUMERICALANALYSIS, [INFO.INFO-DS] Computer Science [cs]/Data Structures and Algorithms [cs.DS], Preconditioning, Approximate inverses, Mathematics::Numerical Analysis, Set (abstract data type), Biconjugate gradient stabilized method, ComputingMethodologies_SYMBOLICANDALGEBRAICMANIPULATION, [INFO.INFO-DC] Computer Science [cs]/Distributed, Parallel, and Cluster Computing [cs.DC], Partition (number theory), ComputingMilieux_MISCELLANEOUS, Sparse matrix, Preconditioner, Applied Mathematics, Numerical analysis, Applied mathematics, Computer Science::Numerical Analysis, Computational Mathematics, [INFO.INFO-DC]Computer Science [cs]/Distributed, Parallel, and Cluster Computing [cs.DC], Algorithm
Abstract: This paper addresses the parallelization of the preconditioned iterative methods that use explicit preconditioners such as approximate inverses. Parallelizing a full step of these methods requires the coefficient and preconditioner matrices to be well partitioned. We first show that different methods impose different partitioning requirements for the matrices. Then we develop hypergraph models to meet those requirements. In particular, we develop models that enable us to obtain partitionings on the coefficient and preconditioner matrices simultaneously. Experiments on a set of unsymmetric sparse matrices show that the proposed models yield effective partitioning results. A parallel implementation of the right preconditioned BiCGStab method on a PC cluster verifies that the theoretical gains obtained by the models hold in practice. © 2007 Society for Industrial and Applied Mathematics.
Published: 2007

321. Revisiting Hypergraph Models for Sparse Matrix Partitioning

Author: Bora Uçar, Cevdet Aykanat, Aykanat, Cevdet, Centre Européen de Recherche et de Formation Avancée en Calcul Scientifique (CERFACS), CERFACS, Department of Computer Engineering (Bilkent-CS), and Bilkent University [Ankara]
Subjects: Parallel computing, Flexibility (engineering), Mathematical models, Hypergraph, Theoretical computer science, Applied Mathematics, [INFO.INFO-DS]Computer Science [cs]/Data Structures and Algorithms [cs.DS], Parallel processing systems, Sparse matrix-vector multiply, Computer simulation, Vectors, ENCODE, Matrix algebra, Theoretical Computer Science, Set (abstract data type), Computational Mathematics, Consistency (database systems), Transformation (function), Matrix partitioning, [INFO.INFO-DC]Computer Science [cs]/Distributed, Parallel, and Cluster Computing [cs.DC], Hypergraph models, Algorithm, ComputingMilieux_MISCELLANEOUS, Sparse matrix, Mathematics
Abstract: We provide an exposition of hypergraph models for parallelizing sparse matrix-vector multiplies. Our aim is to emphasize the expressive power of hypergraph models. First, we set forth an elementary hypergraph model for the parallel matrix-vector multiply based on one-dimensional (1D) matrix partitioning. In the elementary model, the vertices represent the data of a matrix-vector multiply, and the nets encode dependencies among the data. We then apply a recently proposed hypergraph transformation operation to devise models for 1D sparse matrix partitioning. The resulting 1D partitioning models are equivalent to the previously proposed computational hypergraph models and are not meant to be replacements for them. Nevertheless, the new models give us insights into the previous ones and help us explain a subtle requirement, known as the consistency condition, of hypergraph partitioning models. Later, we demonstrate the flexibility of the elementary model on a few 1D partitioning problems that are hard to solve using the previously proposed models. We also discuss extensions of the proposed elementary model to two-dimensional matrix partitioning. © 2007 Society for Industrial and Applied Mathematics.
Published: 2007

322. Aerodynamic Ground Effect in Fruitfly Sized Insect Takeoff

Author: Thomas Engels, Masateru Maeda, Hao Liu, Dmitry Kolomenskiy, Jean-Christophe Nave, Kai Schneider, Laboratoire de Mécanique, Modélisation et Procédés Propres (M2P2), Aix Marseille Université (AMU)-École Centrale de Marseille (ECM)-Centre National de la Recherche Scientifique (CNRS), Centre Européen de Recherche et de Formation Avancée en Calcul Scientifique (CERFACS), Aix Marseille Université (AMU), Technical University of Berlin / Technische Universität Berlin (TU), Department of Mathematics and Statistics [Montréal], McGill University = Université McGill [Montréal, Canada], Centre National de la Recherche Scientifique (CNRS)-École Centrale de Marseille (ECM)-Aix Marseille Université (AMU), CERFACS [Toulouse], Institut national des sciences de l'Univers (INSU - CNRS)-Centre National de la Recherche Scientifique (CNRS), and Technische Universität Berlin (TU)
Subjects: 030110 physiology, 0301 basic medicine, Insecta, Kinematics, Physiology, lcsh:Medicine, Thrust, 01 natural sciences, 010305 fluids & plasmas, [SPI.MECA.MEFL]Engineering Sciences [physics]/Mechanics [physics.med-ph]/Fluids mechanics [physics.class-ph], Ground effect (aerodynamics), Ornithology, Wings, Bird Flight, Medicine and Health Sciences, Wings, Animal, Biomechanics, Animal Anatomy, lcsh:Science, Mathematics, Multidisciplinary, Physics, Classical Mechanics, Aerodynamics, Mechanics, Physics - Fluid Dynamics, Biomechanical Phenomena, Dynamics, Aerodynamic force, Insects, Physical Sciences, Flight (Biology), Research Article, Arthropoda, FOS: Physical sciences, Insect flight, Models, Biological, 03 medical and health sciences, 0103 physical sciences, Animals, Takeoff, Rate of climb, Biological Locomotion, lcsh:R, Fluid Dynamics (physics.flu-dyn), Organisms, Biology and Life Sciences, Invertebrates, Flight, Animal, lcsh:Q, Insect Flight, Zoology
Abstract: International audience; Aerodynamic ground effect in flapping-wing insect flight is of importance to comparative morphologies and of interest to the micro-air-vehicle (MAV) community. Recent studies, however, show apparently contradictory results of either some significant extra lift or power savings, or zero ground effect. Here we present a numerical study of fruitfly sized insect takeoff with a specific focus on the significance of leg thrust and wing kinematics. Flapping-wing takeoff is studied using numerical modelling and high performance computing. The aerodynamic forces are calculated using a three-dimensional Navier--Stokes solver based on a pseudo-spectral method with volume penalization. It is coupled with a flight dynamics solver that accounts for the body weight, inertia and the leg thrust, while only having two degrees of freedom: the vertical and the longitudinal horizontal displacement. The natural voluntary takeoff of a fruitfly is considered as reference. The parameters of the model are then varied to explore possible effects of interaction between the flapping-wing model and the ground plane. These modified takeoffs include cases with decreased leg thrust parameter, and/or with periodic wing kinematics, constant body pitch angle. The results show that the ground effect during natural voluntary takeoff is negligible. In the modified takeoffs, when the rate of climb is slow, the difference in the aerodynamic forces due to the interaction with the ground is up to 6%. Surprisingly, depending on the kinematics, the difference is either positive or negative, in contrast to the intuition based on the helicopter theory, which suggests positive excess lift. This effect is attributed to unsteady wing-wake interactions. A similar effect is found during hovering.
Published: 2015

323. A non-dispersive discontinuous Galerkin method for the simulation of acoustic scattering in complex media

Author: Vanessa Mattesi, Abderrahmane Bendali, Sébastien Tordeux, Hélène Barucq, Julien Diaz, M'Barek Fares, Advanced 3D Numerical Modeling in Geophysics (Magique 3D), Laboratoire de Mathématiques et de leurs Applications [Pau] (LMAP), Université de Pau et des Pays de l'Adour (UPPA)-Centre National de la Recherche Scientifique (CNRS)-Université de Pau et des Pays de l'Adour (UPPA)-Centre National de la Recherche Scientifique (CNRS)-Inria Bordeaux - Sud-Ouest, Institut National de Recherche en Informatique et en Automatique (Inria)-Institut National de Recherche en Informatique et en Automatique (Inria), Institut de Mathématiques de Toulouse UMR5219 (IMT), Institut National des Sciences Appliquées - Toulouse (INSA Toulouse), Institut National des Sciences Appliquées (INSA)-Institut National des Sciences Appliquées (INSA)-Université Toulouse 1 Capitole (UT1), Université Fédérale Toulouse Midi-Pyrénées-Université Fédérale Toulouse Midi-Pyrénées-Université Toulouse - Jean Jaurès (UT2J)-Université Toulouse III - Paul Sabatier (UT3), Université Fédérale Toulouse Midi-Pyrénées-Centre National de la Recherche Scientifique (CNRS), Centre Européen de Recherche et de Formation Avancée en Calcul Scientifique (CERFACS), CERFACS, Université Toulouse Capitole (UT Capitole), Université de Toulouse (UT)-Université de Toulouse (UT)-Institut National des Sciences Appliquées - Toulouse (INSA Toulouse), Institut National des Sciences Appliquées (INSA)-Université de Toulouse (UT)-Institut National des Sciences Appliquées (INSA)-Université Toulouse - Jean Jaurès (UT2J), Université de Toulouse (UT)-Université Toulouse III - Paul Sabatier (UT3), and Université de Toulouse (UT)-Centre National de la Recherche Scientifique (CNRS)
Subjects: Trefftz, Acoustics and Ultrasonics, Discretization, Context (language use), discontinuous Galerkin method, Solver, 01 natural sciences, Domain (mathematical analysis), Finite element method, Mathematics::Numerical Analysis, boundary element method, 03 medical and health sciences, 0302 clinical medicine, Classical mechanics, Arts and Humanities (miscellaneous), Discontinuous Galerkin method, Computer Science::Computational Engineering, Finance, and Science, 0103 physical sciences, Applied mathematics, 030223 otorhinolaryngology, Multipole expansion, 010301 acoustics, Boundary element method, [MATH.MATH-NA]Mathematics [math]/Numerical Analysis [math.NA], Mathematics
Abstract: International audience; In the context of time harmonic acoustic wave propagation, the Discontinuous Galerkin Finite Element Method (DG-FEM) and the Boundary Element Method (BEM) are nowadays classical numerical techniques. On one hand, the DG-FEM is really appropriate to deal with highly heterogeneous media. In comparison with continuous Finite Elements Method (FEM), this method is well adapted to direct solver since its connectivity diagram is significantly smaller than the one of classical FEM. However, it suffers of numerical pollution: the numerical wave does not propagate at the correct velocity. This can be very problematic when this method is used on very large computational domain or at high frequency. On the other hand, the BEM is one of the most efficient method to deal with homogeneous media, especially when accelerated by a multipole method or thanks to the Adaptive Cross Approximation. Moreover, this method is really less affected by numerical pollution. However, BEM is not adapted to heterogeneous media. In this talk, we would like to present a DG-FEM whose shape functions are defined thanks to a BEM. This new numerical discretization method benefits from the advantages of BEM and DG-FEM: low pollution effect, ability to deal with highly heterogeneous media. Numerous simulations will show the efficiency and the accuracy of the method on large domains.
Published: 2015

324. A Parallel Evolution Strategy for an Earth Imaging Problem in Geophysics

Author: Serge Gratton, Luís Nunes Vicente, Youssef Diouane, Xavier Vasseur, Henri Calandra, Département de Mathématiques, Informatique, Automatique (DMIA), Institut Supérieur de l'Aéronautique et de l'Espace (ISAE-SUPAERO), Algorithmes Parallèles et Optimisation (IRIT-APO), Institut de recherche en informatique de Toulouse (IRIT), Université Toulouse 1 Capitole (UT1), Université Fédérale Toulouse Midi-Pyrénées-Université Fédérale Toulouse Midi-Pyrénées-Université Toulouse - Jean Jaurès (UT2J)-Université Toulouse III - Paul Sabatier (UT3), Université Fédérale Toulouse Midi-Pyrénées-Centre National de la Recherche Scientifique (CNRS)-Institut National Polytechnique (Toulouse) (Toulouse INP), Université Fédérale Toulouse Midi-Pyrénées-Université Toulouse 1 Capitole (UT1), Université Fédérale Toulouse Midi-Pyrénées, Institut National Polytechnique (Toulouse) (Toulouse INP), Centre Européen de Recherche et de Formation Avancée en Calcul Scientifique (CERFACS), CERFACS, Universidade de Coimbra [Coimbra], TOTAL S.A., TOTAL FINA ELF, Centre National de la Recherche Scientifique - CNRS (FRANCE), Universidade de Coimbra (PORTUGAL), Institut National Polytechnique de Toulouse - Toulouse INP (FRANCE), Institut Supérieur de l'Aéronautique et de l'Espace - ISAE-SUPAERO (FRANCE), Université Toulouse III - Paul Sabatier - UT3 (FRANCE), Université Toulouse - Jean Jaurès - UT2J (FRANCE), Université Toulouse 1 Capitole - UT1 (FRANCE), and Institut National Polytechnique de Toulouse - INPT (FRANCE)
Subjects: Mathematical optimization, Control and Optimization, High performance computing (HPC), Search space reduction, Aerospace Engineering, 010103 numerical & computational mathematics, Full-waveform inversion, 010502 geochemistry & geophysics, Global convergence, 01 natural sciences, Earth imaging Inverse problem, Optimisation et contrôle, (HPC)Search space reduction, 0101 mathematics, Electrical and Electronic Engineering, Global optimization, Massively parallel, 0105 earth and related environmental sciences, Civil and Structural Engineering, Mathematics, Earth imaging, Mechanical Engineering, Inversion (meteorology), Geophysics, Inverse problem, Solver, Supercomputer, Evolution strategy, Distributed memory, High performance computing, [MATH.MATH-OC]Mathematics [math]/Optimization and Control [math.OC], Algorithm, Software
Abstract: International audience; In this paper we propose a new way to compute a rough approximation solution, to be later used as a warm starting point in a more refined optimization process, for a challenging global optimization problem related to Earth imaging in geophysics. The warm start con- sists of a velocity model that approximately solves a full-waveform inverse problem at low frequency. Our motivation arises from the availability of massively parallel computing plat- forms and the natural parallelization of evolution strategies as global optimization methods for continuous variables.Our first contribution consists of developing a new and efficient parametrization of the velocity models to significantly reduce the dimension of the original optimization space. Our second contribution is to adapt a class of evolution strategies to the specificity of the physical problem at hands where the objective function evaluation is known to be the most expen- sive computational part. A third contribution is the development of a parallel evolution strategy solver, taking advantage of a recently proposed modification of these class of evolu- tionary methods that ensures convergence and promotes better performance under moderate budgets.The numerical results presented demonstrate the effectiveness of the algorithm on a realistic 3D full-waveform inverse problem in geophysics. The developed numerical approach allows us to successfully solve an acoustic full-waveform inversion problem at low frequencies on a reasonable number of cores of a distributed memory computer.
Published: 2015

325. Catalogue of abrupt shifts in Intergovernmental Panel on Climate Change climate models

Author: Marten Scheffer, Chris Huntingford, Victor Brovkin, Martin Claussen, Sebastian Bathiany, Didier Swingedouw, Sybren Drijfhout, Giovanni Sgubin, Claudie Beaulieu, Royal Netherlands Meteorological Institute (KNMI), Max Planck Institute for Meteorology (MPI-M), Max-Planck-Gesellschaft, Centre for Ecology and Hydrology [Wallingford] (CEH), Natural Environment Research Council (NERC), Laboratoire des Sciences du Climat et de l'Environnement [Gif-sur-Yvette] (LSCE), Institut national des sciences de l'Univers (INSU - CNRS)-Université Paris-Saclay-Centre National de la Recherche Scientifique (CNRS)-Commissariat à l'énergie atomique et aux énergies alternatives (CEA)-Université de Versailles Saint-Quentin-en-Yvelines (UVSQ), Centre Européen de Recherche et de Formation Avancée en Calcul Scientifique (CERFACS), CERFACS, and Université de Versailles Saint-Quentin-en-Yvelines (UVSQ)-Commissariat à l'énergie atomique et aux énergies alternatives (CEA)-Institut national des sciences de l'Univers (INSU - CNRS)-Université Paris-Saclay-Centre National de la Recherche Scientifique (CNRS)
Subjects: [SDU.OCEAN]Sciences of the Universe [physics]/Ocean, Atmosphere, Runaway climate change, Aquatic Ecology and Water Quality Management, WIMEK, Multidisciplinary, Global temperature, Global warming, Climate change, Aquatische Ecologie en Waterkwaliteitsbeheer, Radiative forcing, Geography, PNAS Plus, 13. Climate action, Climatology, Greenhouse gas, Abrupt climate change, Life Science, Climate model, [SDU.ENVI]Sciences of the Universe [physics]/Continental interfaces, environment, ComputingMilieux_MISCELLANEOUS
Abstract: Abrupt transitions of regional climate in response to the gradual rise in atmospheric greenhouse gas concentrations are notoriously difficult to foresee. However, such events could be particularly challenging in view of the capacity required for society and ecosystems to adapt to them. We present, to our knowledge, the first systematic screening of the massive climate model ensemble informing the recent Intergovernmental Panel on Climate Change report, and reveal evidence of 37 forced regional abrupt changes in the ocean, sea ice, snow cover, permafrost, and terrestrial biosphere that arise after a certain global temperature increase. Eighteen out of 37 events occur for global warming levels of less than 2°, a threshold sometimes presented as a safe limit. Although most models predict one or more such events, any specific occurrence typically appears in only a few models. We find no compelling evidence for a general relation between the overall number of abrupt shifts and the level of global warming. However, we do note that abrupt changes in ocean circulation occur more often for moderate warming (less than 2°), whereas over land they occur more often for warming larger than 2°. Using a basic proportion test, however, we find that the number of abrupt shifts identified in Representative Concentration Pathway (RCP) 8.5 scenarios is significantly larger than in other scenarios of lower radiative forcing. This suggests the potential for a gradual trend of destabilization of the climate with respect to such shifts, due to increasing global mean temperature change.
Published: 2015

326. A Symmetric Trefftz-DG Formulation based on a Local Boundary Element Method for the Solution of the Helmholtz Equation

Author: Barucq, Hélène, Bendali, Abderrahmane, Fares, M, Mattesi, Vanessa, Tordeux, Sébastien, Advanced 3D Numerical Modeling in Geophysics (Magique 3D), Laboratoire de Mathématiques et de leurs Applications [Pau] (LMAP), Université de Pau et des Pays de l'Adour (UPPA)-Centre National de la Recherche Scientifique (CNRS)-Université de Pau et des Pays de l'Adour (UPPA)-Centre National de la Recherche Scientifique (CNRS)-Inria Bordeaux - Sud-Ouest, Institut National de Recherche en Informatique et en Automatique (Inria)-Institut National de Recherche en Informatique et en Automatique (Inria), Institut de Mathématiques de Toulouse UMR5219 (IMT), Université Toulouse Capitole (UT Capitole), Université de Toulouse (UT)-Université de Toulouse (UT)-Institut National des Sciences Appliquées - Toulouse (INSA Toulouse), Institut National des Sciences Appliquées (INSA)-Université de Toulouse (UT)-Institut National des Sciences Appliquées (INSA)-Université Toulouse - Jean Jaurès (UT2J), Université de Toulouse (UT)-Université Toulouse III - Paul Sabatier (UT3), Université de Toulouse (UT)-Centre National de la Recherche Scientifique (CNRS), Centre Européen de Recherche et de Formation Avancée en Calcul Scientifique (CERFACS), Université de Pau et des Pays de l'Adour (UPPA)-Centre National de la Recherche Scientifique (CNRS), INRIA Bordeaux, Institut National des Sciences Appliquées - Toulouse (INSA Toulouse), Institut National des Sciences Appliquées (INSA)-Institut National des Sciences Appliquées (INSA)-Université Toulouse 1 Capitole (UT1), Université Fédérale Toulouse Midi-Pyrénées-Université Fédérale Toulouse Midi-Pyrénées-Université Toulouse - Jean Jaurès (UT2J)-Université Toulouse III - Paul Sabatier (UT3), Université Fédérale Toulouse Midi-Pyrénées-Centre National de la Recherche Scientifique (CNRS), CERFACS [Toulouse], and Institut national des sciences de l'Univers (INSU - CNRS)-Centre National de la Recherche Scientifique (CNRS)
Subjects: integral equations, Dirichlet-to-Neumann operator, Boundary Element Method, opérateur de Dirichlet-to-Neumann, méthode éléments de frontière, méthode Galerkine Discontinue, formulation variationnelle ultra faible, Pollution numérique, méthode de type Trefftz, Discontinuous Galerkin method, Trefftz method, équations intégrales, dispersion, Helmholtz equation, Equation de Helmholtz, pollution effect, [MATH.MATH-NA]Mathematics [math]/Numerical Analysis [math.NA], ultra-weak variational formulation
Published: 2015

327. Numerical study of flame stability, stabilization and noise in a swirl-stabilized combustor under choked conditions

Author: Lapeyre, Corentin, Centre Européen de Recherche et de Formation Avancée en Calcul Scientifique (CERFACS), ANR, Institut National Polytechnique de Toulouse (INP Toulouse), Thierry Poinsot(poinsot@cerfacs.fr), ANR-11-BS09-0015,DISCERN,Sources directe et indirect en combustion pour la mesure et la réduction du bruit(2011), European Project: 312444,RECORD, Lapeyre, Corentin, BLANC - Sources directe et indirect en combustion pour la mesure et la réduction du bruit - - DISCERN2011 - ANR-11-BS09-0015 - BLANC - VALID, Research in Core Noise Reduction - RECORD - 312444 - INCOMING, and CERFACS
Subjects: [SPI.ACOU]Engineering Sciences [physics]/Acoustics [physics.class-ph], [SPI.ACOU] Engineering Sciences [physics]/Acoustics [physics.class-ph], Simulation aux Grandes Echelles, [SPI.FLUID]Engineering Sciences [physics]/Reactive fluid environment, Thermoacoustic Instabilties, [INFO.INFO-DC] Computer Science [cs]/Distributed, Parallel, and Cluster Computing [cs.DC], Flame Flashback, [SPI.FLUID] Engineering Sciences [physics]/Reactive fluid environment, Combustion Noise, [INFO.INFO-DC]Computer Science [cs]/Distributed, Parallel, and Cluster Computing [cs.DC], Large Eddy Simulation, Bruit de Combustion, Instabilités de Combustion
Abstract: Civil air traffic increase requires to decrease future aircraft emissions. Aeronauticengine combustor technology has evolved towards Lean Prevaporized Premixedcombustion to increase efficiency and reduce noxious emissions. Unfortunately, thistechnology tends to reduce engine robustness, with a decrease in flame stability andstabilization margins, and an increase in combustion noise. Compressible LargeEddy Simulation (LES), a promising numerical approach to describe full combustors,is used in this Ph.D on an academic test rig of a typical modern combustor flamein confined conditions. This investigation gives insight on the effects of full systemdynamics on combustion instabilities, flame flashback and combustion noise. Is showshow these tools can yield understanding of the phenomena controlling flame stabilityand stabilization, which is essential in order to operate future engines safely., Les chambres de combustion aéronautiques s’orientent vers la combustion pauvreprévaporisée prémélangée pour améliorer l’efficacité et réduire les émissions nuisiblesdes moteurs. Malheureusement, cette technologue tend à réduire les marges destabilité et de stabilisation des flammes, tout en augmentant le bruit de combustion.La Simulation aux Grandes Échelles compressible, une approche numériqueprometteuse pour décrire les chambres complètes, est utilisée dans cette thèse sur uncas académique de flamme typique des brûleurs modernes en conditions confinées.L’étude fournit des éléments clés sur l’effet de la dynamique du système completsur les instabilités de combustion, le retour de flamme et le bruit de combustion.Elle montre comment ces outils peuvent aider à comprendre les phénomènes quicontrôlent la stabilité et la stabilisation de flamme, ce qui est essentiel pour opérerles moteurs futurs en toute sécurité.
Published: 2015

328. Integrating top-down and bottom-up approaches to design global change adaptation at the river basin scale

Author: Manuel Pulido-Velazquez, Christian Pagé, Yvan Caballero, Jean-Daniel Rinaudo, Corentin Girard, Universitat Politècnica de València (UPV), Bureau de Recherches Géologiques et Minières (BRGM) (BRGM), Centre Européen de Recherche et de Formation Avancée en Calcul Scientifique (CERFACS), CERFACS, and The study has been financially supported by BRGM-ONEMA joint project on Hydro-economic modelling and by the IMPADAPT project (CGL2013-48424-C2-1-R) from the Spanish ministry MINECO (Ministerio de Economía y Competitividad) with European FEDER funds.
Subjects: INGENIERIA HIDRAULICA, 010504 meteorology & atmospheric sciences, Computer science, Geography, Planning and Development, 0207 environmental engineering, Climate change, [SDU.STU]Sciences of the Universe [physics]/Earth Sciences, Time horizon, 02 engineering and technology, Management, Monitoring, Policy and Law, 01 natural sciences, Top down, 12. Responsible consumption, Resource (project management), 11. Sustainability, Top–down, 020701 environmental engineering, Adaptation (computer science), Climate check, 0105 earth and related environmental sciences, Bottom–up, Global and Planetary Change, Ecology, business.industry, Environmental resource management, Bottom up, 15. Life on land, [SHS.ECO]Humanities and Social Sciences/Economics and Finance, [SDE.ES]Environmental Sciences/Environmental and Society, 6. Clean water, Water resources, Adaptive management, Adaptation measures, 13. Climate action, Sustainability, River basin model, Climate model, business
Abstract: The high uncertainty associated with the effect of global change on water resource systems calls for a better combination of conventional top-down and bottom-up approaches, in order to design robust adaptation plans at the local scale. The methodological framework presented in this article introduces bottom-up meets top-down integrated approach to support the selection of adaptation measures at the river basin level by comprehensively integrating the goals of economic efficiency, social acceptability, environmental sustainability and adaptation robustness. The top-down approach relies on the use of a chain of models to assess the impact of global change on water resources and its adaptive management over a range of climate projections. Future demand scenarios and locally prioritised adaptation measures are identified following a bottom-up approach through a participatory process with the relevant stakeholders and experts. The optimal combinations of adaptation measures are then selected using a hydro-economic model at basin scale for each climate projection. The resulting adaptation portfolios are, finally, climate checked to define a robust least-regret programme of measures based on trade-offs between adaptation costs and the reliability of supply for agricultural demands. This innovative approach has been applied to a Mediterranean basin, the Orb river basin (France). Mid-term climate projections, downscaled from 9 General Climate Models, are used to assess the uncertainty associated with climate projections. Demand evolution scenarios are developed to project agricultural and urban water demands on the 2030 time horizon. The results derived from the integration of the bottom-up and top-down approaches illustrate the sensitivity of the adaptation strategies to the climate projections, and provide an assessment of the trade-offs between the performance of the water resource system and the cost of the adaptation plan to inform local decision-making. The article contributes new methodological elements for the development of an integrated framework for decision-making under climate change uncertainty, advocating an interdisciplinary approach that bridges the gap between bottom-up and top-down approaches., The study has been financially supported by BRGM-ONEMA joint project on Hydro-economic modelling and by the IMPADAPT project (CGL2013-48424-C2-1-R) from the Spanish ministry MINECO (Ministerio de Economia y Competitividad) with European FEDER funds. Corentin Girard is supported by a grant from the University Lecturer Training Program (FPU12/03803) of the Ministry of Education, Culture and Sports of Spain. We also acknowledge the CERFACS for the climate scenarios provided from the SCRATCH 2010 dataset (March 2012 release - http://www.cerfacs.fr/similar to page/work/scratch/). We thank as well the anonymous reviewers and the Editors of Global Environmental Change, for their useful and encouraging comments during the review process.
Published: 2015

329. Status and future of data assimilation in operational oceanography

Author: Gary B. Brassington, Yosuke Fujii, Anthony T. Weaver, Gregory C. Smith, G.A Waagbo, D. J. Lea, Matthew Martin, James Cummings, Kristian Mogensen, Peter R. Oke, Pierre Brasseur, Laurent Bertino, Jean-Michel Lellouche, Jennifer Waters, Magdalena Balmaseda, Charles-Emmanuel Testut, United Kingdom Met Office [Exeter], European Centre for Medium-Range Weather Forecasts (ECMWF), Nansen Environmental and Remote Sensing Center [Bergen] (NERSC), Laboratoire de glaciologie et géophysique de l'environnement (LGGE), Observatoire des Sciences de l'Univers de Grenoble (OSUG), Université Savoie Mont Blanc (USMB [Université de Savoie] [Université de Chambéry])-Institut polytechnique de Grenoble - Grenoble Institute of Technology (Grenoble INP)-Institut national de recherche en sciences et technologies pour l'environnement et l'agriculture (IRSTEA)-Université Joseph Fourier - Grenoble 1 (UJF)-Institut national des sciences de l'Univers (INSU - CNRS)-Centre National de la Recherche Scientifique (CNRS)-Université Grenoble Alpes (UGA)-Université Savoie Mont Blanc (USMB [Université de Savoie] [Université de Chambéry])-Institut polytechnique de Grenoble - Grenoble Institute of Technology (Grenoble INP)-Institut national de recherche en sciences et technologies pour l'environnement et l'agriculture (IRSTEA)-Université Joseph Fourier - Grenoble 1 (UJF)-Institut national des sciences de l'Univers (INSU - CNRS)-Centre National de la Recherche Scientifique (CNRS)-Université Grenoble Alpes (UGA)-Centre National de la Recherche Scientifique (CNRS), Australian Bureau of Meteorology [Melbourne] (BoM), Australian Government, Naval Research Laboratory (NRL), JMA/MRI, Mercator Océan, Société Civile CNRS Ifremer IRD Météo-France SHOM, Commonwealth Scientific and Industrial Research Organisation [Canberra] (CSIRO), Environment and Climate Change Canada, Norwegian Meteorological Institute, Centre Européen de Recherche et de Formation Avancée en Calcul Scientifique (CERFACS), CERFACS, Centre National de la Recherche Scientifique (CNRS)-Institut national des sciences de l'Univers (INSU - CNRS)-Observatoire des Sciences de l'Univers de Grenoble (OSUG), Université Joseph Fourier - Grenoble 1 (UJF)-Institut polytechnique de Grenoble - Grenoble Institute of Technology (Grenoble INP )-Institut national des sciences de l'Univers (INSU - CNRS)-Institut national de recherche en sciences et technologies pour l'environnement et l'agriculture (IRSTEA)-Université Savoie Mont Blanc (USMB [Université de Savoie] [Université de Chambéry])-Centre National de la Recherche Scientifique (CNRS)-Université Joseph Fourier - Grenoble 1 (UJF)-Institut polytechnique de Grenoble - Grenoble Institute of Technology (Grenoble INP )-Institut national de recherche en sciences et technologies pour l'environnement et l'agriculture (IRSTEA)-Université Savoie Mont Blanc (USMB [Université de Savoie] [Université de Chambéry])-Centre National de la Recherche Scientifique (CNRS), and Norwegian Meteorological Institute [Oslo] (MET)
Subjects: Meteorology, Equator, Assimilation (biology), Filter (signal processing), Covariance, Oceanography, Term (time), Data assimilation, 13. Climate action, Climatology, [SDE]Environmental Sciences, Environmental science, Satellite, 14. Life underwater, Altimeter
Abstract: International audience; The GODAE OceanView systems use various data assimilation algorithms, including 3DVar, EnOI, EnKF and the SEEK filter with a fixed basis, using different time windows. The main outputs of the operational data assimilation systems, the increments, have been compared for February 2014 in various regions. The eddy-permitting systems’ increments are similar in a number of the regions, indicating similar forecast errors are being corrected, while the eddy-resolving systems represent smaller-scale structures in the mid-latitude regions investigated and appear to have smaller biases. Monthly average temperature increments show significant SST biases, particularly in the systems which assimilate swath satellite SST data, indicating systematic errors in the surface heat fluxes and the way in which they are propagated vertically by the ocean models. On-going developments to the data assimilation systems include improvements to the specification of error covariances, improving assimilation of data near the equator, and understanding the effect of assimilation on the Atlantic Meridional Overturning Circulation. Longer term developments are expected to include the implementation of more advanced algorithms to make use of flow-dependent error covariance information. Assimilation of new data sources over the coming years, such as wide-swath altimetry, is also expected to improve the accuracy of ocean state estimates and forecasts provided by the GODAE OceanView systems.
Published: 2015

330. Modal structure of a supersonic under-expanded jet

Author: Pérez, Arroyo, Carlos, Daviller, Guillaume, Puigt, Guillaume, Airiau, Christophe, Centre Européen de Recherche et de Formation Avancée en Calcul Scientifique (CERFACS), CERFACS, Institut de mécanique des fluides de Toulouse (IMFT), Université Toulouse III - Paul Sabatier (UT3), Université Fédérale Toulouse Midi-Pyrénées-Université Fédérale Toulouse Midi-Pyrénées-Centre National de la Recherche Scientifique (CNRS)-Institut National Polytechnique (Toulouse) (Toulouse INP), Université Fédérale Toulouse Midi-Pyrénées, Airbus (FRANCE), Centre National d'Études Spatiales - CNES (FRANCE), Centre National de la Recherche Scientifique - CNRS (FRANCE), EDF (FRANCE), Institut National Polytechnique de Toulouse - Toulouse INP (FRANCE), Office National d'Etudes et Recherches Aérospatiales - ONERA (FRANCE), Total (FRANCE), Université Toulouse III - Paul Sabatier - UT3 (FRANCE), Météo France (FRANCE), SAFRAN (FRANCE), Association Française de Mécanique, Institut National Polytechnique de Toulouse - INPT (FRANCE), and Service irevues, irevues
Subjects: jet sousdétendu, Mécanique des fluides, Astrophysics::High Energy Astrophysical Phenomena, modes azimutaux, [PHYS.MECA]Physics [physics]/Mechanics [physics], SGE, [SPI.MECA.MEFL]Engineering Sciences [physics]/Mechanics [physics.med-ph]/Fluids mechanics [physics.class-ph], Physics::Fluid Dynamics, Jet, LES, bruit de choc, aéroacoustique, Aeroacoustics, [PHYS.MECA] Physics [physics]/Mechanics [physics]
Abstract: Colloque avec actes et comité de lecture. Internationale.; International audience; Le bruit de choc est un bruit particulier qui intervient lorsque qu'un jet n'est pas parfaitement détendu. On observe alors des cellules de choc en aval de la tuyère, composées d'onde de compression et de détente. Les interactions entre la turbulence et ces cellules de choc sont responsable de la génération du bruit de choc. Ce bruit se caractérise par une directivité marqué vers l'amont de l'écoulement ainsi qu'une forte intensité. Dans cette étude, nous nous intéressons à l'analyse modale de la structure d'un jet supersonique sous-détendu caractérisé par un nombre de Reynolds Re=UjDj/vj = 10(6), calculé par simulation aux grandes échelles (SGE) à l'aide du code elsA développée par l'ONERA avec l'intégration de schémas d'ordre élevé du CERFACS.
Published: 2015

331. Testing and comparing the Augmented Block Cimmino Distributed solver on some class of applications

Author: BOITEAU, Olivier, DUFF, Iain, GREFFEUILLE, Robin, GUIVARCH, Ronan, RUIZ, Daniel, ZENADI, Mohamed, EDF R&D (EDF R&D), EDF (EDF), Centre Européen de Recherche et de Formation Avancée en Calcul Scientifique (CERFACS), CERFACS, STFC Rutherford Appleton Laboratory (RAL), Science and Technology Facilities Council (STFC), Algorithmes Parallèles et Optimisation (IRIT-APO), Institut de recherche en informatique de Toulouse (IRIT), Université Toulouse 1 Capitole (UT1), Université Fédérale Toulouse Midi-Pyrénées-Université Fédérale Toulouse Midi-Pyrénées-Université Toulouse - Jean Jaurès (UT2J)-Université Toulouse III - Paul Sabatier (UT3), Université Fédérale Toulouse Midi-Pyrénées-Centre National de la Recherche Scientifique (CNRS)-Institut National Polytechnique (Toulouse) (Toulouse INP), Université Fédérale Toulouse Midi-Pyrénées-Université Toulouse 1 Capitole (UT1), Université Fédérale Toulouse Midi-Pyrénées, Institut National Polytechnique (Toulouse) (Toulouse INP), USACM : United States Association for Computational Mechanics, and University of California, San Diego
Subjects: [INFO]Computer Science [cs], ComputingMilieux_MISCELLANEOUS
Abstract: International audience
Published: 2015

332. Adapting cities to climate Change : a systemic modelling approach

Author: Viguie, Vincent, Marchadier, Colette, Adolphe, L, Bonhomme, Marion, Bretagne, Geneviève, De Munck, Cécile, Hallegatte, Stéphane, Hidalgo, Julia, Houet, Thomas, Le Bras, J, Lemonsu, Aude, Long, Nathalie, Masson, Valéry, Moine, Marie-Pierre, Nolorgues, Laurence, Pigeon, Grégoire, Salagnac, Jean-Luc, Zibouche, Kamel, centre international de recherche sur l'environnement et le développement (CIRED), Centre National de la Recherche Scientifique (CNRS)-École des Ponts ParisTech (ENPC)-École des hautes études en sciences sociales (EHESS)-AgroParisTech-Centre de Coopération Internationale en Recherche Agronomique pour le Développement (Cirad), Groupe d'étude de l'atmosphère météorologique (CNRM-GAME), Institut national des sciences de l'Univers (INSU - CNRS)-Météo France-Centre National de la Recherche Scientifique (CNRS), Laboratoire de recherche en architecture (LRA), Université Toulouse - Jean Jaurès (UT2J)-École nationale supérieure d'architecture de Toulouse (ENSA Toulouse), Modèles et simulation pour l'architecture, l'urbanisme et le paysage (MAP), EC ARCHIT NANCY-EC ARCHIT TOULOUSE-EC ARCHIT MARSEILLE-EC ARCHIT LYON-Centre National de la Recherche Scientifique (CNRS)-Ministère de la Culture et de la Communication (MCC)-Institut National des Sciences Appliquées - Strasbourg (INSA Strasbourg), Institut National des Sciences Appliquées (INSA)-Institut National des Sciences Appliquées (INSA), Urban Planning Agency, Toulouse, France, Laboratoire Interdisciplinaire Solidarités, Sociétés, Territoires (LISST), École des hautes études en sciences sociales (EHESS)-Université Toulouse - Jean Jaurès (UT2J)-École Nationale Supérieure de Formation de l'Enseignement Agricole de Toulouse-Auzeville (ENSFEA)-Centre National de la Recherche Scientifique (CNRS), Géographie de l'environnement (GEODE), Université Toulouse - Jean Jaurès (UT2J)-Centre National de la Recherche Scientifique (CNRS), Laboratoire des Sciences du Climat et de l'Environnement [Gif-sur-Yvette] (LSCE), Institut national des sciences de l'Univers (INSU - CNRS)-Université Paris-Saclay-Centre National de la Recherche Scientifique (CNRS)-Commissariat à l'énergie atomique et aux énergies alternatives (CEA)-Université de Versailles Saint-Quentin-en-Yvelines (UVSQ), LIttoral ENvironnement et Sociétés - UMRi 7266 (LIENSs), Université de La Rochelle (ULR)-Centre National de la Recherche Scientifique (CNRS), CERFACS [Toulouse], Institut national des sciences de l'Univers (INSU - CNRS)-Centre National de la Recherche Scientifique (CNRS), Institut d'Aménagement et d'Urbanisme de la Région d'Ile-de-France (IAU Île-de-France), Centre Scientifique et Technique du Bâtiment (CSTB), ANR -Villes et bâtiments durables Ed. 2013, CNRM - Météo France, ANR-13-VBDU-0004,MApUCE,Modélisation Appliquée et droit de l'Urbanisme : Climat urbain et Énergie(2013), Centre de Coopération Internationale en Recherche Agronomique pour le Développement (Cirad)-École des hautes études en sciences sociales (EHESS)-AgroParisTech-École des Ponts ParisTech (ENPC)-Centre National de la Recherche Scientifique (CNRS), Centre national de recherches météorologiques (CNRM), Institut national des sciences de l'Univers (INSU - CNRS)-Observatoire Midi-Pyrénées (OMP), Institut de Recherche pour le Développement (IRD)-Université Toulouse III - Paul Sabatier (UT3), Université de Toulouse (UT)-Université de Toulouse (UT)-Institut national des sciences de l'Univers (INSU - CNRS)-Centre National d'Études Spatiales [Toulouse] (CNES)-Centre National de la Recherche Scientifique (CNRS)-Météo-France -Institut de Recherche pour le Développement (IRD)-Université Toulouse III - Paul Sabatier (UT3), Université de Toulouse (UT)-Université de Toulouse (UT)-Institut national des sciences de l'Univers (INSU - CNRS)-Centre National d'Études Spatiales [Toulouse] (CNES)-Centre National de la Recherche Scientifique (CNRS)-Météo-France -Centre National de la Recherche Scientifique (CNRS), Université Toulouse - Jean Jaurès (UT2J), Université de Toulouse (UT)-Université de Toulouse (UT)-École nationale supérieure d'architecture de Toulouse (ENSA Toulouse), Institut National des Sciences Appliquées - Strasbourg (INSA Strasbourg), Institut National des Sciences Appliquées (INSA)-Institut National des Sciences Appliquées (INSA)-Ministère de la Culture et de la Communication (MCC)-EC ARCHIT NANCY-EC ARCHIT TOULOUSE-EC ARCHIT MARSEILLE-EC ARCHIT LYON-Centre National de la Recherche Scientifique (CNRS), École des hautes études en sciences sociales (EHESS)-Université Toulouse - Jean Jaurès (UT2J), Université de Toulouse (UT)-Université de Toulouse (UT)-École Nationale Supérieure de Formation de l'Enseignement Agricole de Toulouse-Auzeville (ENSFEA)-Centre National de la Recherche Scientifique (CNRS), Université de Toulouse (UT)-Université de Toulouse (UT)-Centre National de la Recherche Scientifique (CNRS), Université de Versailles Saint-Quentin-en-Yvelines (UVSQ)-Commissariat à l'énergie atomique et aux énergies alternatives (CEA)-Institut national des sciences de l'Univers (INSU - CNRS)-Université Paris-Saclay-Centre National de la Recherche Scientifique (CNRS), LIttoral ENvironnement et Sociétés (LIENSs), La Rochelle Université (ULR)-Centre National de la Recherche Scientifique (CNRS), and Centre Européen de Recherche et de Formation Avancée en Calcul Scientifique (CERFACS)
Subjects: modelling, urban change, urban climate, adaptation, [SHS]Humanities and Social Sciences
Abstract: International audience; To answer the climate change challenge, all states have to reduce their greenhouse gas emissions, but also to adopt adaptation measures to limit the negative impacts of global warming on the population, the economy and the environment. The question arises especially for cities.Because of complex interactions between climate change, the evolution of cities and its inhabitants, studying adaptation strategies for cities requires a strong interdisciplinary approach: urban planners, architects, meteorologists, building engineers, economists, social sciences.Our four-step methodology consists firstly of defining interdisciplinary scenarios at several scales influencing the city evolution; secondly of simulating long term city evolution based on socio-economic and land-use models; thirdly of calculating impacts with physical models, and finally of calculating the indicators quantifying the adaptation strategies.Interdisciplinary systemic modelling performs well to evaluate several adaptation strategies for a very broad range of topics. Some of the results obtained for the agglomeration of Paris through our interdisciplinary research projects VURCA and MUSCADE will be discussed:A finding is that Urban planning strategies may have unexpected influence on city expansion when considered on the very long term of the climate change. Another is that the combine effect of global warming and UHI can lead in the future to larger energy consumption in summer than in winter.Indeed, air-conditioning will probably be necessary in 2100, because of expected stronger, and longer, heat waves. Limiting the UHI intensity allows for energy savings, and hence contributes to climate change mitigation. Adaptation strategies exist to limit air-conditioning use, both in time and intensity.Analysis of several vegetation strategies, at several spatial and planning scales (from agricultural practices in the city surroundings to urban trees and green-roofs) have been performed and evaluated. Architectural choices also allow to reduce the UHI. Finally, inhabitants' use and practices seem to be an efficient lever to reduce energy consumption in buildings and its impact on the urban climate.
Published: 2015

333. Numerical simulation of vortex induced drag of elastic swimmers

Author: Engels, T., Kolomenskiy, D., Schneider, K., Sesterhenn, J., Aix Marseille Université (AMU), Technische Universität Berlin (TU), Laboratoire de Mécanique, Modélisation et Procédés Propres (M2P2), Centre National de la Recherche Scientifique (CNRS)-École Centrale de Marseille (ECM)-Aix Marseille Université (AMU), CERFACS [Toulouse], Institut national des sciences de l'Univers (INSU - CNRS)-Centre National de la Recherche Scientifique (CNRS), Department of Numerical Mathematics, Universität der Bundeswehr München [Neubiberg], Constant, Eddy, Technical University of Berlin / Technische Universität Berlin (TU), Aix Marseille Université (AMU)-École Centrale de Marseille (ECM)-Centre National de la Recherche Scientifique (CNRS), and Centre Européen de Recherche et de Formation Avancée en Calcul Scientifique (CERFACS)
Subjects: [PHYS.MECA.MEFL] Physics [physics]/Mechanics [physics]/Fluid mechanics [physics.class-ph], [PHYS.MECA.MEFL]Physics [physics]/Mechanics [physics]/Fluid mechanics [physics.class-ph], ComputingMilieux_MISCELLANEOUS
Abstract: International audience; no abstract
Published: 2015

334. Combined effect of climate change and groundwater abstraction on multi-layer and alluvial aquifers in France

Author: Florence Habets, Pascal Viennot, Charlotte Thierion, Jp. Vergnes, Hamed Ait-Kaci, Yvan Caballero, Philippe Ackerer, Nadia Amraoui, Augeard, B., Besson, F., Jean-Raynald de Dreuzy, Laurent Longuevergne, Martin, E., Morel, T., Regimbeau, F., Dominique Thiery, Jean-Michel Soubeyroux, Milieux Environnementaux, Transferts et Interactions dans les hydrosystèmes et les Sols (METIS), Université Pierre et Marie Curie - Paris 6 (UPMC)-École Pratique des Hautes Études (EPHE), Université Paris sciences et lettres (PSL)-Université Paris sciences et lettres (PSL)-Centre National de la Recherche Scientifique (CNRS), Centre de Géosciences (GEOSCIENCES), Mines Paris - PSL (École nationale supérieure des mines de Paris), Université Paris sciences et lettres (PSL)-Université Paris sciences et lettres (PSL), ANTEA Group, ANTEA, BIPE, Bureau de Recherches Géologiques et Minières (BRGM) (BRGM), Laboratoire d'Hydrologie et de Géochimie de Strasbourg (LHyGeS), Ecole et Observatoire des Sciences de la Terre (EOST), Université de Strasbourg (UNISTRA)-Institut national des sciences de l'Univers (INSU - CNRS)-Centre National de la Recherche Scientifique (CNRS)-Université de Strasbourg (UNISTRA)-Institut national des sciences de l'Univers (INSU - CNRS)-Centre National de la Recherche Scientifique (CNRS)-École Nationale du Génie de l'Eau et de l'Environnement de Strasbourg (ENGEES)-Institut national des sciences de l'Univers (INSU - CNRS)-Centre National de la Recherche Scientifique (CNRS), Office national de l'eau et des milieux aquatiques (ONEMA), Ministère de l'écologie, du développement durable et de l'énergie, Centre national de recherches météorologiques (CNRM), Institut national des sciences de l'Univers (INSU - CNRS)-Observatoire Midi-Pyrénées (OMP), Institut de Recherche pour le Développement (IRD)-Université Toulouse III - Paul Sabatier (UT3), Université de Toulouse (UT)-Université de Toulouse (UT)-Institut national des sciences de l'Univers (INSU - CNRS)-Centre National d'Études Spatiales [Toulouse] (CNES)-Centre National de la Recherche Scientifique (CNRS)-Météo-France -Institut de Recherche pour le Développement (IRD)-Université Toulouse III - Paul Sabatier (UT3), Université de Toulouse (UT)-Université de Toulouse (UT)-Institut national des sciences de l'Univers (INSU - CNRS)-Centre National d'Études Spatiales [Toulouse] (CNES)-Centre National de la Recherche Scientifique (CNRS)-Météo-France -Centre National de la Recherche Scientifique (CNRS), Géosciences Rennes (GR), Université de Rennes (UR)-Institut national des sciences de l'Univers (INSU - CNRS)-Observatoire des Sciences de l'Univers de Rennes (OSUR), Université de Rennes (UR)-Institut national des sciences de l'Univers (INSU - CNRS)-Université de Rennes 2 (UR2)-Centre National de la Recherche Scientifique (CNRS)-Institut National de Recherche pour l’Agriculture, l’Alimentation et l’Environnement (INRAE)-Institut national des sciences de l'Univers (INSU - CNRS)-Université de Rennes 2 (UR2)-Centre National de la Recherche Scientifique (CNRS)-Institut National de Recherche pour l’Agriculture, l’Alimentation et l’Environnement (INRAE)-Centre National de la Recherche Scientifique (CNRS), Centre Européen de Recherche et de Formation Avancée en Calcul Scientifique (CERFACS), Centre National de la Recherche Scientifique (CNRS)-École pratique des hautes études (EPHE), Université Paris sciences et lettres (PSL)-Université Paris sciences et lettres (PSL)-Université Pierre et Marie Curie - Paris 6 (UPMC), MINES ParisTech - École nationale supérieure des mines de Paris, Meteo France, Toulouse, France, Centre National de la Recherche Scientifique (CNRS)-Observatoire des Sciences de l'Univers de Rennes (OSUR)-Institut national des sciences de l'Univers (INSU - CNRS)-Université de Rennes 1 (UR1), Université de Rennes (UNIV-RENNES)-Université de Rennes (UNIV-RENNES), and CERFACS
Subjects: climate change, alluvial aquifer, Climate Models, [SDU.STU]Sciences of the Universe [physics]/Earth Sciences, groundwater resources
Abstract: International audience; Although nowadays groundwater resources are mostly affected by increasing water abstraction, they will have toface the impact of climate change. Even in a temperate climate as the one in northern France these two driverswill have strong impact on the aquifers. Evolution of groundwater resource is most often studied based onevolution of the rainfall infiltration that is assumed to be the aquifer recharge, although river-aquifer and multilayeraquifer exchanges are also part of the recharge and can only be estimated using a hydrogeological model.Moreover, providing a change of the piezometric level is usually not found to be meaningful by stakeholder as a 1meter variation can have different impact depending on the hydrogeological context. Therefore, in this study, toprovide greater insight into the impact of groundwater, two new indicators are used: the evolution of the extensionof groundwater-fed wetlands and the frequency with which a crisis piezometric head is exceeded. The crisispiezometric levels are used locally by stakeholders and as soon as the observed piezometric heads fall below theselevels, actions are taken to preserve the water resource. For the present study, the local crisis piezometric heads were extended to the whole studied basins, the Seine andUpper Rhine Graben basins. The results show that the two basins under study are not affected in the same way by climate and groundwaterabstraction changes. The Seine multi-layer aquifers are projected to suffer from a substantial decrease in rainfall infiltration (about 20%), while the decrease is lower in the Upper Rhine Graben aquifer (about 6%).In 2050, the extension of groundwater-fed wetlands is expected to lose about 900m2/km2, while the crisispiezometric heads are expected to be exceeded about 40% and 26% of the time on average on the Seine and UpperRhine Graben aquifers, respectively. The reduction of the groundwater abstraction has a large impact locally but isnot efficient enough to overcome the impact of climate change, although the impact is more sensitive on the Upper Rhine Graben than on the Seine, and particularly on the extension of wetlands and low flow.Sensitivity to the parameters that drive the river-aquifer exchange was found to be second order compared to theuncertainty due to the climate model in the Upper Rhine Graben, although these parameters have a considerable impact on present-day estimation of the aquifer balance. The two indicators are found to be highly useful to discuss the impact of climate change on groundwater with stakeholders.In order to be able to extent such studies to the whole aquifers of France, and to have a survey of such impact as soon as new downscaled projections are available, the AquiFR project is bringing together hydrogeologicalapplications used by stakeholder in a common plateform that will be based at Météo-France
Published: 2015

335. Comparison of climate change impacts on the recharge of two karst systems computing different modelling approaches

Author: Caballero, Yvan, Zerouali, Laila, Ladouche, B., Lanini, Sandra, Seguin, Jean-Jacques, Charlier, Jean-Baptiste, Cadilhac, Laurent, Maréchal, Jean-Christophe, Pages, C., Bureau de Recherches Géologiques et Minières (BRGM) (BRGM), Agence de l'eau Rhône Méditérranée Corse, Centre Européen de Recherche et de Formation Avancée en Calcul Scientifique (CERFACS), and CERFACS
Subjects: climate change, [SDE.MCG]Environmental Sciences/Global Changes, Karst aquifer system, recharge modelling, [SDU.STU]Sciences of the Universe [physics]/Earth Sciences, groundwater resources, [SDU.STU.HY]Sciences of the Universe [physics]/Earth Sciences/Hydrology
Abstract: International audience; Karst systems constitute aquifers in which infiltration and groundwater flows are generally complex processes and are characterized by limited knowledge in terms of geometry and structure. Nonetheless, they often represent interesting groundwater resources, some of them being subjected to intensive exploitation and others non exploited due to their poor understanding. In the future, it is likely that climate change impact on water resources will increase the interest for such a kind of aquifers due to their strong infiltration and storage capacity, in a broad context of higher water scarcity.The Lez and the Lison karst systems in Southern and Eastern France, respectively, provide 2 examples of such systems of several km² under two contrasted climate conditions, the first one being heavily exploited. This study presents a comparative climate change assessment onboth karst systems. Nine climate scenarios corresponding to the Fourth assessment report of the IPCC (SRES A1B scenario), downscaled using weather-type methods by the CERFACS, have been applied to various recharge modelling approaches, as standard analytical solutions of recharge estimation and soil-water balance models. Results are compared and discussed in order to assess the influence on climate change impacts of i) the climate conditions(geographic location), ii) the groundwater exploitation and iii) the modelling approach.
Published: 2015

336. Changements Environnementaux Côtiers : Impact de la hausse du niveau de la mer

Author: Cazenave, Anny, Le Cozannet, Gonéri, Salas Y Melia, David, Woppelmann, Guy, Walker, Patrice, Pronost, Ronan, Rogel, Philippe, Laboratoire d'études en Géophysique et océanographie spatiales (LEGOS), Institut de Recherche pour le Développement (IRD)-Université Toulouse III - Paul Sabatier (UT3), Université Fédérale Toulouse Midi-Pyrénées-Université Fédérale Toulouse Midi-Pyrénées-Institut national des sciences de l'Univers (INSU - CNRS)-Observatoire Midi-Pyrénées (OMP), Météo France-Centre National d'Études Spatiales [Toulouse] (CNES)-Université Fédérale Toulouse Midi-Pyrénées-Centre National de la Recherche Scientifique (CNRS)-Institut de Recherche pour le Développement (IRD)-Météo France-Centre National d'Études Spatiales [Toulouse] (CNES)-Centre National de la Recherche Scientifique (CNRS)-Institut de Recherche pour le Développement (IRD)-Centre National de la Recherche Scientifique (CNRS), Bureau de Recherches Géologiques et Minières (BRGM) (BRGM), Groupe d'étude de l'atmosphère météorologique (CNRM-GAME), Institut national des sciences de l'Univers (INSU - CNRS)-Météo France-Centre National de la Recherche Scientifique (CNRS), LIttoral ENvironnement et Sociétés - UMRi 7266 (LIENSs), Université de La Rochelle (ULR)-Centre National de la Recherche Scientifique (CNRS), CREOCEAN, Service Hydrographique et Océanographique de la Marine (SHOM), Ministère de la Défense, Centre Européen de Recherche et de Formation Avancée en Calcul Scientifique (CERFACS), CERFACS, and Agence Nationale de la Recherche
Subjects: [SDU.STU]Sciences of the Universe [physics]/Earth Sciences
Abstract: Maison de la Chimie, side event de la conférence "Our Common Future under Climate Change"; National audience; L’une des conséquences déjà perceptibles du changement climatique est le réchauffement des océans et la fonte des glaces continentales. Ces processus ont causé une hausse du niveau de la mer de l’ordre de 25 cm en moyenne entre 1900 et 2010. Mais depuis 2 dernières décennies, la vitesse d’élévation s’est accélérée et atteint 3.2mm/an actuellement. Loin d’être uniforme, cette élévation du niveau de la mer présente une forte variabilité régionale, qui peut localement être amplifiée par des subsidences du sol. L’une des conséquences attendues de la hausse de la mer est une aggravation de l’érosion de certain types de littoraux et la submersion permanente de zones côtières basses. Dans le projet CECILE soutenu par l’ANR entre 2010 et 2013, 7 équipes françaises se sont regroupées pour étudier l’impact de la hausse de la mer depuis 1950 sur l’évolution du trait de côte dans plusieurs régions de la planète : Pacifique tropical ouest, Océan Indien, région Caraïbes, Europe de l’ouest, etc. Si dans certaines régions, la hausse régionale a suivi l’élévation moyenne globale, dans d’autres, comme le Pacifique tropical ouest, le niveau marin s’est élevé 2 à 3 fois plus vite. D’où la question : peut-on distinguer dors et déjà des évolutions côtières différentes en fonction de la vitesse de remontée du niveau marin spécifique à chaque région ? Les résultats indiquent que dans la plupart des cas, les effets de l’élévation du niveau de la mer sur l’évolution littorale sont masqués par ceux des facteurs hydrométéorologiques (tempêtes, cyclones, vagues, courants…) et anthropiques (défenses côtières, modification des apports sédimentaires par les fleuves induit par des activités humaines). Si pour les décennies passées, l’érosion des littoraux n’est pas causée par la hausse de la mer mais plutôt par la combinaison des activités humaines et des phénomènes naturels, il est probable que dans le futur, l’élévation attendue de la mer (entre 50cm et 1m en moyenne globale en 2100 pour le scénario RCP 8.5 du 5ème rapport du GIEC, avec de fortes disparités régionales, en particulier une amplification dans les tropiques) deviendra un facteur important (lors d’évènements extrêmes, notamment), voire même dominant dans plusieurs régions côtières du globe. Dans le contexte de l’adaptation au changement climatique, il est urgent de développer au plus vite des études d’impact de la hausse du niveau de la mer au 21ème siècle, à partir de projections régionales précises combinées à des modèles d’évolution et de vulnérabilité des zones côtières en réponse aux forçages climatique et anthropique. Les équipes françaises (dont celles du projet CECILE) disposent du savoir-faire nécessaire pour aborder ces questions dont l’importance pour les sociétés humaines n’est plus à démontrer.
Published: 2015

337. Experimental and numerical study of modulation of ionization front propagation velocity in µs helium plasma gun discharge with nitrogen admixture

Author: Darny, Thibault, Robert, Eric, Pechereau, François, Viegas, Pedro, Dozias, Sebatien, Bourdon, Anne, Pouvesle, Jean-Michel, Groupe de recherches sur l'énergétique des milieux ionisés (GREMI), Université d'Orléans (UO)-Centre National de la Recherche Scientifique (CNRS), CERFACS [Toulouse], Institut national des sciences de l'Univers (INSU - CNRS)-Centre National de la Recherche Scientifique (CNRS), Laboratoire de Physique des Plasmas (LPP), Université Paris-Sud - Paris 11 (UP11)-Université Pierre et Marie Curie - Paris 6 (UPMC)-Observatoire de Paris, Université Paris sciences et lettres (PSL)-Université Paris sciences et lettres (PSL)-École polytechnique (X)-Sorbonne Université (SU)-Université Paris-Saclay-Centre National de la Recherche Scientifique (CNRS), APR PLASMEDNORM, IPCS, ANR-10-BLAN-0930,PAMPA,Plasmas: Microjets à Pression Atmosphérique(2010), Centre Européen de Recherche et de Formation Avancée en Calcul Scientifique (CERFACS), and Université Paris sciences et lettres (PSL)-Université Paris sciences et lettres (PSL)-École polytechnique (X)-Université Paris-Saclay-Centre National de la Recherche Scientifique (CNRS)
Subjects: [SPI]Engineering Sciences [physics], Atmospheric Plasma, [SPI.PLASMA]Engineering Sciences [physics]/Plasmas, Plasma jet, Plasma gun
Abstract: International audience; This work reports on experimental and numerical analysis of the effect of nitrogen admixture on the development of helium based atmospheric pressure discharge produced by the Plasma Gun in long dielectric tubes. Besides, the drastic extension of discharge propagation length, reactive species generation can be tailored to specific applications while keeping electric field properties quite constant. This might afford unique opportunities to study specific action of the different plasma components for biomedical applications. Good agreement was found with recently developed model calculations, emphasising the key role of plasma kinetics on the ionization level of the plasma stream connecting the ionization front with the powered electrode of the DBD reactor.
Published: 2015

338. 2D time−resolved measurement and modeling of electric fields associated with atmospheric pressure plasma streams propagation in dielectric capillaries

Author: Darny, Thibault, Robert, Eric, Pechereau, François, Dozias, Sebatien, Bourdon, Anne, Pouvesle, Jean-Michel, Groupe de recherches sur l'énergétique des milieux ionisés (GREMI), Université d'Orléans (UO)-Centre National de la Recherche Scientifique (CNRS), Centre Européen de Recherche et de Formation Avancée en Calcul Scientifique (CERFACS), Laboratoire de Physique des Plasmas (LPP), Université Paris-Sud - Paris 11 (UP11)-Université Pierre et Marie Curie - Paris 6 (UPMC)-Observatoire de Paris, Université Paris sciences et lettres (PSL)-Université Paris sciences et lettres (PSL)-École polytechnique (X)-Université Paris-Saclay-Centre National de la Recherche Scientifique (CNRS), APR PLASMEDNORM, IPCS, ANR-10-BLAN-0930,PAMPA,Plasmas: Microjets à Pression Atmosphérique(2010), POUVESLE, Jean-Michel, BLANC - Plasmas: Microjets à Pression Atmosphérique - - PAMPA2010 - ANR-10-BLAN-0930 - BLANC - VALID, CERFACS [Toulouse], Institut national des sciences de l'Univers (INSU - CNRS)-Centre National de la Recherche Scientifique (CNRS), and Université Paris sciences et lettres (PSL)-Université Paris sciences et lettres (PSL)-École polytechnique (X)-Sorbonne Université (SU)-Université Paris-Saclay-Centre National de la Recherche Scientifique (CNRS)
Subjects: [SPI]Engineering Sciences [physics], [SPI] Engineering Sciences [physics], Atmospheric Plasma, [SPI.PLASMA]Engineering Sciences [physics]/Plasmas, Plasma Jet, [SPI.PLASMA] Engineering Sciences [physics]/Plasmas, Plasma Gun, ComputingMilieux_MISCELLANEOUS, Plasma modeling
Abstract: International audience
Published: 2015

339. A model-tested North Atlantic Oscillation reconstruction for the past millennium

Author: Mathieu Casado, Pascal Yiou, Pablo Ortega, Flavio Lehner, Didier Swingedouw, Valérie Masson-Delmotte, Christoph C. Raible, NCAS-Climate [Reading], Department of Meteorology [Reading], University of Reading (UOR)-University of Reading (UOR), Universität Bern [Bern], Centre Européen de Recherche et de Formation Avancée en Calcul Scientifique (CERFACS), CERFACS, Laboratoire des Sciences du Climat et de l'Environnement [Gif-sur-Yvette] (LSCE), Institut national des sciences de l'Univers (INSU - CNRS)-Université Paris-Saclay-Centre National de la Recherche Scientifique (CNRS)-Commissariat à l'énergie atomique et aux énergies alternatives (CEA)-Université de Versailles Saint-Quentin-en-Yvelines (UVSQ), Glaces et Continents, Climats et Isotopes Stables (GLACCIOS), Institut national des sciences de l'Univers (INSU - CNRS)-Université Paris-Saclay-Centre National de la Recherche Scientifique (CNRS)-Commissariat à l'énergie atomique et aux énergies alternatives (CEA)-Université de Versailles Saint-Quentin-en-Yvelines (UVSQ)-Institut national des sciences de l'Univers (INSU - CNRS)-Université Paris-Saclay-Centre National de la Recherche Scientifique (CNRS)-Commissariat à l'énergie atomique et aux énergies alternatives (CEA)-Université de Versailles Saint-Quentin-en-Yvelines (UVSQ), Extrèmes : Statistiques, Impacts et Régionalisation (ESTIMR), Universität Bern [Bern] (UNIBE), Université de Versailles Saint-Quentin-en-Yvelines (UVSQ)-Commissariat à l'énergie atomique et aux énergies alternatives (CEA)-Institut national des sciences de l'Univers (INSU - CNRS)-Université Paris-Saclay-Centre National de la Recherche Scientifique (CNRS), and Université de Versailles Saint-Quentin-en-Yvelines (UVSQ)-Commissariat à l'énergie atomique et aux énergies alternatives (CEA)-Institut national des sciences de l'Univers (INSU - CNRS)-Université Paris-Saclay-Centre National de la Recherche Scientifique (CNRS)-Université de Versailles Saint-Quentin-en-Yvelines (UVSQ)-Commissariat à l'énergie atomique et aux énergies alternatives (CEA)-Institut national des sciences de l'Univers (INSU - CNRS)-Université Paris-Saclay-Centre National de la Recherche Scientifique (CNRS)
Subjects: [SDU.OCEAN]Sciences of the Universe [physics]/Ocean, Atmosphere, geography, Multidisciplinary, geography.geographical_feature_category, 010504 meteorology & atmospheric sciences, Meteorology, Atmospheric circulation, Climate, Northern Hemisphere, Climate change, Storm, Models, Theoretical, 010502 geochemistry & geophysics, 01 natural sciences, Proxy (climate), Volcano, 13. Climate action, North Atlantic oscillation, Climatology, Predictability, [SDU.ENVI]Sciences of the Universe [physics]/Continental interfaces, environment, Atlantic Ocean, ComputingMilieux_MISCELLANEOUS, 0105 earth and related environmental sciences
Abstract: The North Atlantic Oscillation (NAO) is the major source of variability in winter atmospheric circulation in the Northern Hemisphere, with large impacts on temperature, precipitation and storm tracks, and therefore also on strategic sectors such as insurance, renewable energy production, crop yields and water management. Recent developments in dynamical methods offer promise to improve seasonal NAO predictions, but assessing potential predictability on multi-annual timescales requires documentation of past low-frequency variability in the NAO. A recent bi-proxy NAO reconstruction spanning the past millennium suggested that long-lasting positive NAO conditions were established during medieval times, explaining the particularly warm conditions in Europe during this period; however, these conclusions are debated. Here, we present a yearly NAO reconstruction for the past millennium, based on an initial selection of 48 annually resolved proxy records distributed around the Atlantic Ocean and built through an ensemble of multivariate regressions. We validate the approach in six past-millennium climate simulations, and show that our reconstruction outperforms the bi-proxy index. The final reconstruction shows no persistent positive NAO during the medieval period, but suggests that positive phases were dominant during the thirteenth and fourteenth centuries. The reconstruction also reveals that a positive NAO emerges two years after strong volcanic eruptions, consistent with results obtained from models and satellite observations for the Mt Pinatubo eruption in the Philippines.
Published: 2015

340. Uncertainty Quantification of Thermoacoustic Instabilities in a Swirled Stabilized Combustor

Author: Aissatou Ndiaye, Michaël Bauerheim, Franck Nicoud, Stéphane Moreau, Airbus (FRANCE), Centre National d'Études Spatiales - CNES (FRANCE), EDF (FRANCE), Office National d'Etudes et Recherches Aérospatiales - ONERA (FRANCE), Total (FRANCE), Météo France (FRANCE), SAFRAN (FRANCE), Université de Montpellier (FRANCE), Université de Sherbrooke (CANADA), Institut Montpelliérain Alexander Grothendieck - IMAG (Montpellier, France), Centre Européen de Recherche et de Formation Avancée en Calcul Scientifique (CERFACS), CERFACS, Université de Sherbrooke (UdeS), Institut Montpelliérain Alexander Grothendieck (IMAG), and Université de Montpellier (UM)-Centre National de la Recherche Scientifique (CNRS)
Subjects: Engineering, 020209 energy, Monte Carlo method, Combustion chambers, Combustion, 02 engineering and technology, 01 natural sciences, Transfer function, Acoustique, 010305 fluids & plasmas, Swirled, symbols.namesake, Control theory, 0103 physical sciences, 0202 electrical engineering, electronic engineering, information engineering, Uncertainty quantification, [SPI.ACOU]Engineering Sciences [physics]/Acoustics [physics.class-ph], UQ, Operating point, business.industry, Thermoacoustics, Mechanics, Solver, Instabilities, Helmholtz free energy, Combustor, symbols, business
Abstract: International audience; Combustion instabilities can develop in modern gas-turbines as large amplitude pressure oscillations coupled with heat release fluctuations. In extreme cases, they lead to irreversible damage which can destroy the combustor. Prediction and control of all acoustic modes of the configuration at the design stage are therefore required to avoid these instabilities. This is a challenging task because of the large number of parameters involved. This situation becomes even more complex when considering uncertainties of the underlying models and input parameters. The forward uncertainty quantification problem is addressed in the case of a single swirled burner combustor. First, a Helmholtz solver is used to analyze the thermoacoustic modes of the combustion chamber. The Flame Transfer Function measured experimentally is used as a flame model for the Helmholtz solver. Then, the frequency of oscillation and the growth rate of the first thermoacoustic mode are computed in 24 different operating points. Comparisons between experimental and numerical results show good agreements except for modes which are marginally stable/unstable. The main reason is that the uncertainties can arbitrary change the nature of these modes (stable vs unstable); in other words, the usual mode classification stable/unstable must be replaced by a more continuous description such as the risk factor, i.e. the probability for a mode to be unstable given the uncertainties on the input parameters. To do so, a Monte Carlo analysis is performed using 4000 Helmholtz simulations of a single experimental operating point but with random perturbations on the FTF parameters. This allows the computation of the risk factor associated to this acoustic mode. Finally, the analysis of the Monte Carlo database suggests that a reduced two-step UQ strategy may be efficient to deal with thermoacoustics in such a system. First, two bilinear surrogate models are tuned from a moderate number of Helmholtz solutions (a few tens). Then, these algebraic models are used to perform a Monte Carlo analysis at reduced cost and approximate the risk factor of the mode. The accuracy and efficiency of this reduced UQ strategy are assessed by comparing the reference risk factor given by the full Monte Carlo database and the approximate risk factor obtained by the surrogate models. It shows a good agreement which proves that reduced efficient methods can be used to predict unstable modes.
Published: 2015

341. Assessment of the Indirect Combustion Noise Generated in a Transonic High-Pressure Turbine Stage

Author: Franck Nicoud, Laurent Gicquel, Dimitrios Papadogiannis, Gaofeng Wang, Florent Duchaine, Stéphane Moreau, Centre Européen de Recherche et de Formation Avancée en Calcul Scientifique (CERFACS), CERFACS, Université de Sherbrooke (UdeS), GAUS, Institut Montpelliérain Alexander Grothendieck (IMAG), and Université de Montpellier (UM)-Centre National de la Recherche Scientifique (CNRS)
Subjects: Engineering, Stator, business.industry, Mechanical Engineering, Acoustics, Energy Engineering and Power Technology, Aerospace Engineering, Acoustic wave, 7. Clean energy, Turbine, [INFO.INFO-MO]Computer Science [cs]/Modeling and Simulation, law.invention, Physics::Fluid Dynamics, Fuel Technology, Nuclear Energy and Engineering, law, Dynamic mode decomposition, Combustor, Combustion chamber, business, Transonic, Large eddy simulation
Abstract: International audience; Indirect combustion noise, generated by the acceleration and distortion of entropy waves through the turbine stages, has been shown to be the dominant noise source of gas turbines at low-frequencies and to impact the thermoacoustic behavior of the combustor. In the present work, indirect combustion noise generation is evaluated in the realistic, fully 3D transonic high-pressure turbine stage MT1 using large eddy simulations (LESs). An analysis of the basic flow and the different turbine noise generation mechanisms is performed for two configurations: one with a steady inflow and a second with a pulsed inlet, where a plane entropy wave train at a given frequency is injected before propagating across the stage generating indirect noise. The noise is evaluated through the dynamic mode decomposition (DMD) of the flow field. It is compared with the previous 2D simulations of a similar stator/rotor configuration, as well as with the compact theory of Cumpsty and Marble. Results show that the upstream propagating entropy noise is reduced due to the choked turbine nozzle guide vane. Downstream acoustic waves are found to be of similar strength to the 2D case, highlighting the potential impact of indirect combustion noise on the overall noise signature of the engine.
Published: 2015

342. Le changement climatique sur le bassin de la Seine

Author: Habets, Florence, Viennot, Pascal, Boe, Julien, Caballero, Yvan, Déqué, Michel, Ducharne, Agnès, Gallois, Nicolas, Martin, Eric, Pagé, Christian, Philippe, Élodie, Thiery, Dominique, Verjus, Philippe, Milieux Environnementaux, Transferts et Interactions dans les hydrosystèmes et les Sols (METIS), École Pratique des Hautes Études (EPHE), Université Paris sciences et lettres (PSL)-Université Paris sciences et lettres (PSL)-Institut national des sciences de l'Univers (INSU - CNRS)-Sorbonne Université (SU)-Centre National de la Recherche Scientifique (CNRS), Centre de Géosciences (GEOSCIENCES), Mines Paris - PSL (École nationale supérieure des mines de Paris), Université Paris sciences et lettres (PSL)-Université Paris sciences et lettres (PSL), Sci Univers CERFACS, URA 1875, Centre National de la Recherche Scientifique (CNRS), Bureau de Recherches Géologiques et Minières (BRGM) (BRGM), Centre national de recherches météorologiques (CNRM), Institut national des sciences de l'Univers (INSU - CNRS)-Observatoire Midi-Pyrénées (OMP), Institut de Recherche pour le Développement (IRD)-Université Toulouse III - Paul Sabatier (UT3), Université de Toulouse (UT)-Université de Toulouse (UT)-Institut national des sciences de l'Univers (INSU - CNRS)-Centre National d'Études Spatiales [Toulouse] (CNES)-Centre National de la Recherche Scientifique (CNRS)-Météo-France -Institut de Recherche pour le Développement (IRD)-Université Toulouse III - Paul Sabatier (UT3), Université de Toulouse (UT)-Université de Toulouse (UT)-Institut national des sciences de l'Univers (INSU - CNRS)-Centre National d'Études Spatiales [Toulouse] (CNES)-Centre National de la Recherche Scientifique (CNRS)-Météo-France -Centre National de la Recherche Scientifique (CNRS), Université Pierre et Marie Curie - Paris 6 (UPMC)-École Pratique des Hautes Études (EPHE), Université Paris sciences et lettres (PSL)-Université Paris sciences et lettres (PSL)-Centre National de la Recherche Scientifique (CNRS), Centre Européen de Recherche et de Formation Avancée en Calcul Scientifique (CERFACS), DRIEE Ile-de-France, École pratique des hautes études (EPHE), Université Paris sciences et lettres (PSL)-Université Paris sciences et lettres (PSL)-Sorbonne Université (SU)-Centre National de la Recherche Scientifique (CNRS), MINES ParisTech - École nationale supérieure des mines de Paris, Groupe d'étude de l'atmosphère météorologique (CNRM-GAME), Institut national des sciences de l'Univers (INSU - CNRS)-Météo France-Centre National de la Recherche Scientifique (CNRS), Université Pierre et Marie Curie - Paris 6 (UPMC)-École pratique des hautes études (EPHE), and CERFACS
Subjects: [SDE.IE]Environmental Sciences/Environmental Engineering, [SDE.MCG]Environmental Sciences/Global Changes, [SDU.STU.HY]Sciences of the Universe [physics]/Earth Sciences/Hydrology, ComputingMilieux_MISCELLANEOUS
Abstract: International audience
Published: 2015

343. Enrichissement de préconditionneurs pour la résolution de systèmes linéaires symétriques indéfinis

Author: Mercier, Sylvain, Gratton, Serge, Tardieu, Nicolas, Vasseur, Xavier, Laboratoire de Génie Electrique de Grenoble (G2ELab), Université Joseph Fourier - Grenoble 1 (UJF)-Centre National de la Recherche Scientifique (CNRS)-Institut Polytechnique de Grenoble - Grenoble Institute of Technology-Institut polytechnique de Grenoble - Grenoble Institute of Technology (Grenoble INP ), Algorithmes Parallèles et Optimisation (IRIT-APO), Institut de recherche en informatique de Toulouse (IRIT), Université Toulouse 1 Capitole (UT1), Université Fédérale Toulouse Midi-Pyrénées-Université Fédérale Toulouse Midi-Pyrénées-Université Toulouse - Jean Jaurès (UT2J)-Université Toulouse III - Paul Sabatier (UT3), Université Fédérale Toulouse Midi-Pyrénées-Centre National de la Recherche Scientifique (CNRS)-Institut National Polytechnique (Toulouse) (Toulouse INP), Université Fédérale Toulouse Midi-Pyrénées-Université Toulouse 1 Capitole (UT1), Université Fédérale Toulouse Midi-Pyrénées, Institut National Polytechnique (Toulouse) (Toulouse INP), EDF R&D (EDF R&D), EDF (EDF), Centre Européen de Recherche et de Formation Avancée en Calcul Scientifique (CERFACS), CERFACS, and CSMA
Subjects: [PHYS.MECA]Physics [physics]/Mechanics [physics], système symétrique indéfini, point-selle, Préconditionnement
Abstract: International audience; Dans cette communication est présentée une méthode d'enrichissement de préconditionneurs dans le cadre des méthodes itératives de Krylov pour une séquence de systèmes linéaires symétriques indéfinis. En supposant que les matrices varient légèrement, l'idée est de récupérer de l'information spectrale approchée lors de la résolution du premier système afin d'accélérer la convergence des suivants. Cette méthode est illustrée par deux études industrielles d'EDF nécessitant la résolution de problèmes de type point-selle, effectuées à l'aide du logiciel Code_Aster.
Published: 2015

344. Intrinsic Variability of Sea Level from Global Ocean Simulations: Spatiotemporal Scales

Author: Guillaume Sérazin, Jean-Marc Molines, Laurent Terray, Thierry Penduff, Sandy Grégorio, Bernard Barnier, Laboratoire de glaciologie et géophysique de l'environnement (LGGE), Centre National de la Recherche Scientifique (CNRS)-Institut national des sciences de l'Univers (INSU - CNRS)-Observatoire des Sciences de l'Univers de Grenoble (OSUG), Université Joseph Fourier - Grenoble 1 (UJF)-Institut polytechnique de Grenoble - Grenoble Institute of Technology (Grenoble INP )-Institut national des sciences de l'Univers (INSU - CNRS)-Institut national de recherche en sciences et technologies pour l'environnement et l'agriculture (IRSTEA)-Université Savoie Mont Blanc (USMB [Université de Savoie] [Université de Chambéry])-Centre National de la Recherche Scientifique (CNRS)-Université Joseph Fourier - Grenoble 1 (UJF)-Institut polytechnique de Grenoble - Grenoble Institute of Technology (Grenoble INP )-Institut national de recherche en sciences et technologies pour l'environnement et l'agriculture (IRSTEA)-Université Savoie Mont Blanc (USMB [Université de Savoie] [Université de Chambéry])-Centre National de la Recherche Scientifique (CNRS), P.P. Shirshov Institute of Oceanology (SIO), Russian Academy of Sciences [Moscow] (RAS), Institut des Géosciences de l’Environnement (IGE), Institut national des sciences de l'Univers (INSU - CNRS)-Centre National de la Recherche Scientifique (CNRS)-Institut polytechnique de Grenoble - Grenoble Institute of Technology (Grenoble INP )-Institut de Recherche pour le Développement (IRD)-Université Grenoble Alpes [2016-2019] (UGA [2016-2019]), Centre Européen de Recherche et de Formation Avancée en Calcul Scientifique (CERFACS), CERFACS, Observatoire des Sciences de l'Univers de Grenoble (OSUG), Université Joseph Fourier - Grenoble 1 (UJF)-Institut polytechnique de Grenoble - Grenoble Institute of Technology (Grenoble INP )-Institut national des sciences de l'Univers (INSU - CNRS)-Institut national de recherche en sciences et technologies pour l'environnement et l'agriculture (IRSTEA)-Université Savoie Mont Blanc (USMB [Université de Savoie] [Université de Chambéry])-Centre National de la Recherche Scientifique (CNRS)-Université Joseph Fourier - Grenoble 1 (UJF)-Institut polytechnique de Grenoble - Grenoble Institute of Technology (Grenoble INP )-Institut national des sciences de l'Univers (INSU - CNRS)-Institut national de recherche en sciences et technologies pour l'environnement et l'agriculture (IRSTEA)-Université Savoie Mont Blanc (USMB [Université de Savoie] [Université de Chambéry])-Centre National de la Recherche Scientifique (CNRS)-Centre National de la Recherche Scientifique (CNRS), and Institut de Recherche pour le Développement (IRD)-Institut polytechnique de Grenoble - Grenoble Institute of Technology (Grenoble INP )-Institut national des sciences de l'Univers (INSU - CNRS)-Centre National de la Recherche Scientifique (CNRS)-Université Grenoble Alpes [2016-2019] (UGA [2016-2019])
Subjects: [SDU.OCEAN]Sciences of the Universe [physics]/Ocean, Atmosphere, Atmospheric Science, Ocean current, Magnitude (mathematics), Seasonality, medicine.disease, Gulf Stream, 13. Climate action, Climatology, medicine, Environmental science, Hindcast, Spatial variability, 14. Life underwater, Altimeter, Sea level
Abstract: In high-resolution ocean general circulation models (OGCMs), as in process-oriented models, a substantial amount of interannual to decadal variability is generated spontaneously by oceanic nonlinearities: that is, without any variability in the atmospheric forcing at these time scales. The authors investigate the temporal and spatial scales at which this intrinsic oceanic variability has the strongest imprints on sea level anomalies (SLAs) using a ° global OGCM, by comparing a “hindcast” driven by the full range of atmospheric time scales with its counterpart forced by a repeated climatological atmospheric seasonal cycle. Outputs from both simulations are compared within distinct frequency–wavenumber bins. The fully forced hindcast is shown to reproduce the observed distribution and magnitude of low-frequency SLA variability very accurately. The small-scale (L < 6°) SLA variance is, at all time scales, barely sensitive to atmospheric variability and is almost entirely of intrinsic origin. The high-frequency (mesoscale) part and the low-frequency part of this small-scale variability have almost identical geographical distributions, supporting the hypothesis of a nonlinear temporal inverse cascade spontaneously transferring kinetic energy from high to low frequencies. The large-scale (L > 12°) low-frequency variability is mostly related to the atmospheric variability over most of the global ocean, but it is shown to remain largely intrinsic in three eddy-active regions: the Gulf Stream, Kuroshio, and Antarctic Circumpolar Current (ACC). Compared to its ¼° predecessor, the authors’ ° OGCM is shown to yield a stronger intrinsic SLA variability, at both mesoscale and low frequencies.
Published: 2015

345. A Wideband Fast Multipole Method for the Helmholtz Kernel: Theoretical Developments

Author: Francis Collino, Stphanie Chaillat, Propagation des Ondes : Étude Mathématique et Simulation (POEMS), Inria Saclay - Ile de France, Institut National de Recherche en Informatique et en Automatique (Inria)-Institut National de Recherche en Informatique et en Automatique (Inria)-Unité de Mathématiques Appliquées (UMA), École Nationale Supérieure de Techniques Avancées (ENSTA Paris)-École Nationale Supérieure de Techniques Avancées (ENSTA Paris)-Centre National de la Recherche Scientifique (CNRS), CERFACS, and Centre Européen de Recherche et de Formation Avancée en Calcul Scientifique (CERFACS)
Subjects: Helmholtz equation, Fast multipole method, Fast Multipole Method, Plane wave, Broadband, symbols.namesake, [SPI]Engineering Sciences [physics], Optics, [PHYS.MECA.SOLID]Physics [physics]/Mechanics [physics]/Solid mechanics [physics.class-ph], Applied mathematics, [MATH.MATH-AP]Mathematics [math]/Analysis of PDEs [math.AP], Wideband, Mathematics, business.industry, Plane wave expansion, Computational Mathematics, Computational Theory and Mathematics, Modeling and Simulation, Kernel (statistics), Helmholtz free energy, symbols, business, Quadrature errors, Interpolation
Abstract: International audience; This work presents a new Fast Multipole Method (FMM) based on plane wave expansions (PWFMM), combining the advantages of the low and high frequency formulations. We revisit the method of Greengard et al. [1] devoted to the low frequency regime and based on the splitting of the Green's function into a propagative and an evanescent part. More precisely, we give an explicit formula of the filtered translation function for the propagative part, we derive a new formula for the evanescent part and we provide a new interpolation algorithm. At all steps, we check the accuracy of the method by providing error estimates. These theoretical developments are used to propose a wideband FMM based entirely on plane wave expansions. The numerical efficiency and accuracy of this broadband PWFMM are illustrated with a numerical example.
Published: 2015

346. Large Eddy Simulation of transverse acoustic activity in a 42-injector rocket engine

Author: Urbano, Annafederica, Selle, Laurent, Staffelbach, Gabriel, Cuenot, Bénédicte, Thomas, Schmitt, Ducruix, Sebastien, Candel, Sebastien, Institut de mécanique des fluides de Toulouse (IMFT), Université Toulouse III - Paul Sabatier (UT3), Université Fédérale Toulouse Midi-Pyrénées-Université Fédérale Toulouse Midi-Pyrénées-Centre National de la Recherche Scientifique (CNRS)-Institut National Polytechnique (Toulouse) (Toulouse INP), Université Fédérale Toulouse Midi-Pyrénées, Centre Européen de Recherche et de Formation Avancée en Calcul Scientifique (CERFACS), CERFACS, Laboratoire d'Énergétique Moléculaire et Macroscopique, Combustion (EM2C), and Université Paris Saclay (COmUE)-Centre National de la Recherche Scientifique (CNRS)-CentraleSupélec
Subjects: [SPI]Engineering Sciences [physics], [SPI.FLUID]Engineering Sciences [physics]/Reactive fluid environment, ComputingMilieux_MISCELLANEOUS
Abstract: International audience
Published: 2015

347. Interannual variability (1979-2013) of the North-Western Mediterranean deep water mass formation: past observation reanalysis and coupled ocean-atmosphere high-resolution modelling

Author: Somot, Samuel, Houpert, Loïc, Sevault, Florence, Testor, Pierre, Bosse, Anthony, Durrieu de Madron, Xavier, Dubois, Clotilde, Herrmann, Marine, Waldman, Robin, Bouin, Marie-Noëlle, Cassou, Christophe, Centre national de recherches météorologiques (CNRM), Institut national des sciences de l'Univers (INSU - CNRS)-Observatoire Midi-Pyrénées (OMP), Institut de Recherche pour le Développement (IRD)-Université Toulouse III - Paul Sabatier (UT3), Université de Toulouse (UT)-Université de Toulouse (UT)-Institut national des sciences de l'Univers (INSU - CNRS)-Centre National d'Études Spatiales [Toulouse] (CNES)-Centre National de la Recherche Scientifique (CNRS)-Météo-France -Institut de Recherche pour le Développement (IRD)-Université Toulouse III - Paul Sabatier (UT3), Université de Toulouse (UT)-Université de Toulouse (UT)-Institut national des sciences de l'Univers (INSU - CNRS)-Centre National d'Études Spatiales [Toulouse] (CNES)-Centre National de la Recherche Scientifique (CNRS)-Météo-France -Centre National de la Recherche Scientifique (CNRS), Variabilité de l'Océan et de la Glace de mer (VOG), Laboratoire d'Océanographie et du Climat : Expérimentations et Approches Numériques (LOCEAN), Muséum national d'Histoire naturelle (MNHN)-Institut de Recherche pour le Développement (IRD)-Université Pierre et Marie Curie - Paris 6 (UPMC)-Institut national des sciences de l'Univers (INSU - CNRS)-Centre National de la Recherche Scientifique (CNRS)-Institut Pierre-Simon-Laplace (IPSL (FR_636)), École normale supérieure - Paris (ENS-PSL), Université Paris sciences et lettres (PSL)-Université Paris sciences et lettres (PSL)-Université de Versailles Saint-Quentin-en-Yvelines (UVSQ)-Commissariat à l'énergie atomique et aux énergies alternatives (CEA)-Institut national des sciences de l'Univers (INSU - CNRS)-Université Paris Diderot - Paris 7 (UPD7)-École polytechnique (X)-Centre National d'Études Spatiales [Toulouse] (CNES)-Sorbonne Université (SU)-Centre National de la Recherche Scientifique (CNRS)-École normale supérieure - Paris (ENS-PSL), Université Paris sciences et lettres (PSL)-Université Paris sciences et lettres (PSL)-Université de Versailles Saint-Quentin-en-Yvelines (UVSQ)-Commissariat à l'énergie atomique et aux énergies alternatives (CEA)-Université Paris Diderot - Paris 7 (UPD7)-École polytechnique (X)-Centre National d'Études Spatiales [Toulouse] (CNES)-Sorbonne Université (SU)-Centre National de la Recherche Scientifique (CNRS)-Muséum national d'Histoire naturelle (MNHN)-Institut de Recherche pour le Développement (IRD)-Université Pierre et Marie Curie - Paris 6 (UPMC)-Institut national des sciences de l'Univers (INSU - CNRS)-Centre National de la Recherche Scientifique (CNRS)-Institut Pierre-Simon-Laplace (IPSL (FR_636)), Université Paris sciences et lettres (PSL)-Université Paris sciences et lettres (PSL)-Université de Versailles Saint-Quentin-en-Yvelines (UVSQ)-Commissariat à l'énergie atomique et aux énergies alternatives (CEA)-Université Paris Diderot - Paris 7 (UPD7)-École polytechnique (X)-Centre National d'Études Spatiales [Toulouse] (CNES)-Sorbonne Université (SU)-Centre National de la Recherche Scientifique (CNRS), Centre de Formation et de Recherche sur les Environnements Méditérranéens (CEFREM), Université de Perpignan Via Domitia (UPVD)-Institut national des sciences de l'Univers (INSU - CNRS)-Centre National de la Recherche Scientifique (CNRS), Ecole Nationale Supérieure d'Informatique pour l'Industrie et l'Entreprise (ENSIIE), Centre d'enseignement Cnam Paris (CNAM Paris), Conservatoire National des Arts et Métiers [CNAM] (CNAM), HESAM Université - Communauté d'universités et d'établissements Hautes écoles Sorbonne Arts et métiers université (HESAM)-HESAM Université - Communauté d'universités et d'établissements Hautes écoles Sorbonne Arts et métiers université (HESAM), Laboratoire d'études en Géophysique et océanographie spatiales (LEGOS), Université de Toulouse (UT)-Université de Toulouse (UT)-Institut national des sciences de l'Univers (INSU - CNRS)-Observatoire Midi-Pyrénées (OMP), Université de Toulouse (UT)-Université de Toulouse (UT)-Institut national des sciences de l'Univers (INSU - CNRS)-Centre National d'Études Spatiales [Toulouse] (CNES)-Centre National de la Recherche Scientifique (CNRS)-Météo-France -Institut de Recherche pour le Développement (IRD)-Institut national des sciences de l'Univers (INSU - CNRS)-Centre National d'Études Spatiales [Toulouse] (CNES)-Centre National de la Recherche Scientifique (CNRS)-Météo-France -Centre National de la Recherche Scientifique (CNRS), Centre Européen de Recherche et de Formation Avancée en Calcul Scientifique (CERFACS), Groupe d'étude de l'atmosphère météorologique (CNRM-GAME), Institut national des sciences de l'Univers (INSU - CNRS)-Météo France-Centre National de la Recherche Scientifique (CNRS), Institut de Recherche pour le Développement (IRD)-Centre National de la Recherche Scientifique (CNRS)-Institut national des sciences de l'Univers (INSU - CNRS)-Université Pierre et Marie Curie - Paris 6 (UPMC)-Muséum national d'Histoire naturelle (MNHN)-Institut Pierre-Simon-Laplace (IPSL (FR_636)), École normale supérieure - Paris (ENS Paris), Université Paris sciences et lettres (PSL)-Université Paris sciences et lettres (PSL)-Université de Versailles Saint-Quentin-en-Yvelines (UVSQ)-Commissariat à l'énergie atomique et aux énergies alternatives (CEA)-Institut national des sciences de l'Univers (INSU - CNRS)-Université Paris Diderot - Paris 7 (UPD7)-École polytechnique (X)-Centre National d'Études Spatiales [Toulouse] (CNES)-Sorbonne Université (SU)-Centre National de la Recherche Scientifique (CNRS)-École normale supérieure - Paris (ENS Paris), Université Paris sciences et lettres (PSL)-Université Paris sciences et lettres (PSL)-Université de Versailles Saint-Quentin-en-Yvelines (UVSQ)-Commissariat à l'énergie atomique et aux énergies alternatives (CEA)-Université Paris Diderot - Paris 7 (UPD7)-École polytechnique (X)-Centre National d'Études Spatiales [Toulouse] (CNES)-Sorbonne Université (SU)-Centre National de la Recherche Scientifique (CNRS)-Institut de Recherche pour le Développement (IRD)-Centre National de la Recherche Scientifique (CNRS)-Institut national des sciences de l'Univers (INSU - CNRS)-Université Pierre et Marie Curie - Paris 6 (UPMC)-Muséum national d'Histoire naturelle (MNHN)-Institut Pierre-Simon-Laplace (IPSL (FR_636)), Université de Perpignan Via Domitia (UPVD)-Centre National de la Recherche Scientifique (CNRS), Université Fédérale Toulouse Midi-Pyrénées-Université Fédérale Toulouse Midi-Pyrénées-Institut national des sciences de l'Univers (INSU - CNRS)-Observatoire Midi-Pyrénées (OMP), Météo France-Centre National d'Études Spatiales [Toulouse] (CNES)-Université Fédérale Toulouse Midi-Pyrénées-Centre National de la Recherche Scientifique (CNRS)-Institut de Recherche pour le Développement (IRD)-Météo France-Centre National d'Études Spatiales [Toulouse] (CNES)-Centre National de la Recherche Scientifique (CNRS)-Institut de Recherche pour le Développement (IRD)-Centre National de la Recherche Scientifique (CNRS), and CERFACS
Subjects: [PHYS.PHYS.PHYS-GEO-PH]Physics [physics]/Physics [physics]/Geophysics [physics.geo-ph], ComputingMilieux_MISCELLANEOUS
Abstract: International audience
Published: 2015

348. Integrating hydrological features and genetically validated occurrence data in occupancy modeling of an endemic and endangered semi-aquatic mammal species, Galemys pyrenaicus, in a Pyrenean catchment

Author: François Gillet, Frank D'Amico, Stéphane Aulagnier, Mélanie Némoz, F. Blanc, Marjorie Biffi, José-Miguel Sánchez-Pérez, Laëtitia Buisson, Johan Michaux, Pascal Laffaille, Vincent Lacaze, Christian Pagé, Aurélien Besnard, Anaïs Charbonnel, Sabine Sauvage, Conservatoire d'Espaces Naturels Midi-Pyrénées - CEN MP (FRANCE), Laboratoire Ecologie Fonctionnelle et Environnement (LEFE), Institut Ecologie et Environnement (INEE), Centre National de la Recherche Scientifique (CNRS)-Centre National de la Recherche Scientifique (CNRS)-Université Toulouse III - Paul Sabatier (UT3), Université de Toulouse (UT)-Université de Toulouse (UT)-Observatoire Midi-Pyrénées (OMP), Institut de Recherche pour le Développement (IRD)-Université Toulouse III - Paul Sabatier (UT3), Université de Toulouse (UT)-Université de Toulouse (UT)-Institut national des sciences de l'Univers (INSU - CNRS)-Centre National d'Études Spatiales [Toulouse] (CNES)-Centre National de la Recherche Scientifique (CNRS)-Météo-France -Institut de Recherche pour le Développement (IRD)-Institut national des sciences de l'Univers (INSU - CNRS)-Centre National d'Études Spatiales [Toulouse] (CNES)-Centre National de la Recherche Scientifique (CNRS)-Météo-France -Centre National de la Recherche Scientifique (CNRS)-Institut National Polytechnique (Toulouse) (Toulouse INP), Université de Toulouse (UT), Laboratoire de Mathématiques et de leurs Applications [Pau] (LMAP), Université de Pau et des Pays de l'Adour (UPPA)-Centre National de la Recherche Scientifique (CNRS), Centre d’Ecologie Fonctionnelle et Evolutive (CEFE), Université Paul-Valéry - Montpellier 3 (UPVM)-Institut National de la Recherche Agronomique (INRA)-Centre international d'études supérieures en sciences agronomiques (Montpellier SupAgro)-École Pratique des Hautes Études (EPHE), Université Paris sciences et lettres (PSL)-Université Paris sciences et lettres (PSL)-Université de Montpellier (UM)-Centre National de la Recherche Scientifique (CNRS)-Institut de Recherche pour le Développement (IRD [France-Sud])-Institut national d’études supérieures agronomiques de Montpellier (Montpellier SupAgro), Unité de recherche Comportement et Ecologie de la Faune Sauvage (CEFS), Institut National de la Recherche Agronomique (INRA), Laboratoire de Génétique des Microorganismes, Université de Liège - Gembloux, Association des Naturalistes de l'Ariège (FRANCE), Centre Européen de Recherche et de Formation Avancée en Calcul Scientifique (CERFACS), ANRT [2011/1018], EDF (Electricite de France), European Union (FEDER), Laboratoire Ecologie Fonctionnelle et Environnement (ECOLAB), Université Toulouse III - Paul Sabatier (UT3), Université Fédérale Toulouse Midi-Pyrénées-Université Fédérale Toulouse Midi-Pyrénées-Institut Ecologie et Environnement (INEE), Centre National de la Recherche Scientifique (CNRS)-Centre National de la Recherche Scientifique (CNRS)-Institut National Polytechnique (Toulouse) (Toulouse INP), Université Fédérale Toulouse Midi-Pyrénées-Observatoire Midi-Pyrénées (OMP), Météo France-Centre National d'Études Spatiales [Toulouse] (CNES)-Université Fédérale Toulouse Midi-Pyrénées-Centre National de la Recherche Scientifique (CNRS)-Institut de Recherche pour le Développement (IRD)-Météo France-Centre National d'Études Spatiales [Toulouse] (CNES)-Centre National de la Recherche Scientifique (CNRS)-Institut de Recherche pour le Développement (IRD)-Centre National de la Recherche Scientifique (CNRS), Centre National de la Recherche Scientifique (CNRS)-Université de Montpellier (UM)-École pratique des hautes études (EPHE), Université Paris sciences et lettres (PSL)-Université Paris sciences et lettres (PSL)-Centre international d'études supérieures en sciences agronomiques (Montpellier SupAgro)-Institut National de la Recherche Agronomique (INRA)-Université Paul-Valéry - Montpellier 3 (UPVM)-Institut national d’études supérieures agronomiques de Montpellier (Montpellier SupAgro), Institut national d'enseignement supérieur pour l'agriculture, l'alimentation et l'environnement (Institut Agro)-Institut national d'enseignement supérieur pour l'agriculture, l'alimentation et l'environnement (Institut Agro)-Institut de Recherche pour le Développement (IRD [France-Sud]), CERFACS, Université Fédérale Toulouse Midi-Pyrénées-Université Fédérale Toulouse Midi-Pyrénées-Observatoire Midi-Pyrénées (OMP), Université Fédérale Toulouse Midi-Pyrénées-Centre National de la Recherche Scientifique (CNRS)-Institut National Polytechnique (Toulouse) (Toulouse INP), Université Fédérale Toulouse Midi-Pyrénées, Biogéographie et Écologie des Vertébrés (EPHE), École pratique des hautes études (EPHE), Conservatoire Régional des Espaces Naturels Midi-Pyrénées - CREN (FRANCE), Centre de Coopération Internationale en Recherche Agronomique - CIRAD (FRANCE), Centre National de la Recherche Scientifique - CNRS (FRANCE), Institut National Polytechnique de Toulouse - Toulouse INP (FRANCE), Montpellier SupAgro (FRANCE), Université Toulouse III - Paul Sabatier - UT3 (FRANCE), Université de Liège (BELGIUM), Université de Montpellier 1 (FRANCE), Université de Montpellier 2 (FRANCE), Ecole Pratique des Hautes Etudes - EPHE (FRANCE), Université de Pau et des Pays de l'Adour - UPPA (FRANCE), Université de Montpellier 3 (FRANCE), Laboratoire Ecologie fonctionnelle et Environnement - EcoLab (Toulouse, France), Centre Européen de Recherche et Formation Avancées en Calcul Scientifique - CERFACS (Toulouse, France), and Institut National Polytechnique de Toulouse - INPT (FRANCE)
Subjects: 0106 biological sciences, Occupancy, [SDV]Life Sciences [q-bio], Endangered species, 010603 evolutionary biology, 01 natural sciences, [SDV.EE.ECO]Life Sciences [q-bio]/Ecology, environment/Ecosystems, Soil and water assessment tool, 14. Life underwater, [SDU.STU.HY]Sciences of the Universe [physics]/Earth Sciences/Hydrology, Galemys pyrenaicus, Pyrenean desman, Hydrologie, Ecology, Evolution, Behavior and Systematics, ComputingMilieux_MISCELLANEOUS, Nature and Landscape Conservation, Ecologie, Environnement, Markovian site occupancy model, [SDV.EE]Life Sciences [q-bio]/Ecology, environment, Habitat fragmentation, biology, Ecology, [SDE.IE]Environmental Sciences/Environmental Engineering, 010604 marine biology & hydrobiology, 15. Life on land, biology.organism_classification, Environmental niche modelling, Desman, Detection, Geography, Ecosystèmes, Habitat, Habitat use, 13. Climate action, Threatened species, [SDE]Environmental Sciences
Abstract: International audience; As freshwater habitats are among the most endangered, there is an urgent need to identify critical areas for conservation, especially those that are home to endangered species. The Pyrenean desman (Galemys pyrenaicus) is a semi-aquatic mammal whose basic ecological requirements are largely unknown, hindering adequate conservation planning even though it is considered as a threatened species. Species distribution modelling is challenging for freshwater species. Indeed, the complexity of aquatic ecosystems (e.g., linear and hierarchical ordering) must be taken into account as well as imperfect sampling. High-quality and relevant hydrological descriptors should also be used. To understand the influence of environmental covariates on the occupancy and detection of the Pyrenean desman, we combine both a robust sign-survey data set (i.e. with genetic validation ensuring true presence information) and a hydrological model to simulate the flow regime across a whole catchment. Markovian site-occupancy analysis, taking into account sign detection and based on spatially adjacent replicates, indicated a positive influence of heterogeneity of substrate and shelters, and a negative influence of flow variability on Pyrenean desman detection. This valuable information should help to improve monitoring programs for this endangered species. Our results also highlighted a spatially clustered distribution and a positive influence of stream flow and number of tributaries on occupancy. Hence, modifications of flow regime (e.g. hydropower production, irrigation, climate change) and habitat fragmentation appear to be major threats for this species, altering the connectivity between tributaries and the mainstream river as well as between adjacent sub-catchments.
Published: 2015

349. JAGUAR: a New CFD Code Dedicated to Massively Parallel High-Order LES Computations on Complex Geometry

Author: Adrien Cassagne, Jean-François Boussuge, Nadège Villedieu, Guillaume Puigt, Apos Ast, Isabelle D., Aurelien Genot, Centre Européen de Recherche et de Formation Avancée en Calcul Scientifique (CERFACS), CERFACS, and Cassagne, Adrien
Subjects: [INFO.INFO-DC] Computer Science [cs]/Distributed, Parallel, and Cluster Computing [cs.DC], [PHYS.MECA.MEFL] Physics [physics]/Mechanics [physics]/Fluid mechanics [physics.class-ph], [PHYS.MECA.MEFL]Physics [physics]/Mechanics [physics]/Fluid mechanics [physics.class-ph], [INFO.INFO-DC]Computer Science [cs]/Distributed, Parallel, and Cluster Computing [cs.DC]
Abstract: International audience; LES of industrial flows is associated with geometrical complexity and requires high order schemes to minimize dissipation and dispersion. To tackle these two issues it is necessary to use unstructured grids and High Performance Computing algorithms. In this context, CERFACS initiated two years ago the development of a new CFD code called JAGUAR based on a mathematical framework leading to high-level capability for LES. In this paper, many topics for HPC are introduced and solved in order to obtain the best code performance.
Published: 2015

350. Shock-cell noise of supersonic underexpanded jets

Author: Pérez-Arroyo, Carlos, Daviller, Guillaume, Puigt, Guillaume, Airiau, Christophe, CERFACS, Institut de mécanique des fluides de Toulouse (IMFT), Université Toulouse III - Paul Sabatier (UT3), Université Fédérale Toulouse Midi-Pyrénées-Université Fédérale Toulouse Midi-Pyrénées-Centre National de la Recherche Scientifique (CNRS)-Institut National Polytechnique (Toulouse) (Toulouse INP), Université Fédérale Toulouse Midi-Pyrénées, Centre National de la Recherche Scientifique - CNRS (FRANCE), Institut National Polytechnique de Toulouse - INPT (FRANCE), Université Toulouse III - Paul Sabatier - UT3 (FRANCE), Centre Européen de Recherche et Formation Avancées en Calcul Scientifique - CERFACS (FRANCE), Institut de Mécanique des Fluides de Toulouse - IMFT (Toulouse, France), and Institut National Polytechnique de Toulouse - Toulouse INP (FRANCE)
Subjects: Physics::Fluid Dynamics, Jet, Mécanique des fluides, Astrophysics::High Energy Astrophysical Phenomena, LES, Aeroacoustics, [PHYS.MECA.MEFL]Physics [physics]/Mechanics [physics]/Fluid mechanics [physics.class-ph]
Abstract: International audience; Shock-cell noise is a particular noise that appears in imperfectly expanded jets. Under these expansion conditions a series of expansions and compressions appear following a shock-cell type structure. The interaction between the vortices developed at the lip of the nozzle and the shock-cells generates what is known as shock-cell noise. This noise has the particularity to be propagated upstream with a higher intensity. This publication will focus on the shock-cell noise generated by an axisymmetric under-expanded 10 to the power of 6 Reynolds single jet. The LES computations are carried out using the elsA code developed by ONERA and extended by CERFACS with high-order compact schemes. They are validated against experimental results. The LES simulation is initialized with a RANS solution where the nozzle exit conditions are imposed. Even though no inflow forcing is applied, good agreement is obtained in terms of flow structures and broadband shock-cell noise that is propagated to the farfield by means of the Ffowcs-Williams & Hawkings analogy.
Published: 2015

Catalog

Books, media, physical & digital resources

See catalog results

Searchworks

Select search scope, currently: Articles Catalog books, media & more in Jio Institute collections Articles journal articles & other e-resources

Search

Search Constraints

Refine your results

Search Limiters

Topic

Publication Year Range

Language

Publication Type

Journal

Region

Database

Publisher

966 results on '"CERFACS"'

Search Results

Catalog

Select search scope, currently: Articles

Catalog

books, media & more in Jio Institute collections

Articles

journal articles & other e-resources