111 results on '"Yves Brunet"'
Search Results
2. Simulating the effects of regional forest cover changes on mid-latitude boundary-layer clouds
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Gaëtan Noual, Yves Brunet, Patrick Le Moigne, and Christine Lac
- Abstract
Evidence has been provided that land-cover changes such as deforestation can have an impact on cloudiness and precipitation. However, conflicting results have been obtained at different scales and places, highlighting our poor understanding of the physical processes involved. Here we focus on mesoscale summer cloudiness in a temperate region, as influenced by a large forest massif (the Landes forest in France). Our study is based on an up-to-date atmosphere-surface mesoscale model (Meso-NH coupled with SURFEX). Based on observational data, we first optimise the model configuration for our purpose, and show that with a 500 m horizontal resolution we can successfully simulate the higher summer cloud cover observed over the forest, compared to its surroundings. Secondly, we investigate the physical processes leading to cloud formation in a representative case study. Based on a comparative analysis of diagnostics and budgets over forest and non-forest areas, we find that the larger sensible heat flux over the forest and its higher roughness are the main drivers of cloudiness, enhancing vertical velocity and boundary-layer mixing. Third, we simulate the impact of the 2009 Klaus storm that led to the loss of about one third of the trees. Considering fifteen representative convective summer days, we show that the model simulates well the resulting decrease in summer cloudiness that was reported in a previous study based on satellite observations. As a complementary tool, the mesoscale simulations allow to quantify the impacts of the Klaus storm windthrough on the diurnal cycle of the boundary layer. more...
- Published
- 2023
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Catalog
3. Chapitre 11 : Impact de la végétation sur le microclimat urbain et la qualité de l’air
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Yves Brunet
- Published
- 2020
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4. Turbulent flow in plant canopies: historical perspective and overview
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Yves Brunet, Interactions Sol Plante Atmosphère (UMR ISPA), and Ecole Nationale Supérieure des Sciences Agronomiques de Bordeaux-Aquitaine (Bordeaux Sciences Agro)-Institut National de Recherche pour l’Agriculture, l’Alimentation et l’Environnement (INRAE) more...
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Canopy ,Atmospheric Science ,010504 meteorology & atmospheric sciences ,Turbulence ,Roughness sublayer ,Flow (psychology) ,Microclimate ,15. Life on land ,Surface boundary layer ,Atmospheric sciences ,01 natural sciences ,Field (geography) ,Wind speed ,Atmosphere ,Plant canopy ,Plane mixing layer ,13. Climate action ,[SDE]Environmental Sciences ,Atmospheric instability ,Environmental science ,Turbulent shear flow ,0105 earth and related environmental sciences - Abstract
Studying the microclimate of plant canopies has long motivated scientists in various research fields such as agronomy, ecology or silviculture, and almost a century has passed since the first measurements of wind speed in a forest stand were published in the scientific literature. The behaviour of wind in canopies is an essential component of their microclimate, which largely conditions the rate of exchange of heat, water vapour, and other gases and particles of interest with the atmosphere. This review examines the evolution of our understanding of turbulent flow in plant canopies, focussing on the period that covers the last fifty years (1970-2020). We first describe how our knowledge and ideas have evolved since canopy flow became a topic of interest, and show how the 1970s was a pivotal decade in this field. Until then, canopy turbulence was considered to result from the superposition of standard surface-layer turbulence and small-scale turbulence generated in the wakes of plant elements. However, it was progressively found that the flow in plant canopies is dominated by large coherent structures, giving canopy turbulence unique characteristics. We thus describe the particular nature and structure of canopy flows, based on experimental observations accumulated over several decades. We show how canopy turbulence was reconsidered on the basis of a now widely-accepted analogy with a plane mixing layer, and we examine the significance of a key parameter, the "canopy-shear length scale". Investigating the effects of canopy density and atmospheric stability, we then discuss the extent of the mixing-layer analogy and the limits of our current understanding of canopy turbulence. Finally, we review the modelling tools used in this field and show how their development has evolved to date to meet our needs. In conclusion, we present a historical summary of the evolution of this research field and suggest future directions. more...
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- 2020
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5. Trade Credit as an Option to Acquire Financing
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Volodymyr Babich, Pierre-Yves Brunet, and Tarik Aouam
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Finance ,0209 industrial biotechnology ,business.industry ,02 engineering and technology ,Current period ,Management Science and Operations Research ,020901 industrial engineering & automation ,Trade credit ,Supply chain finance ,Credit history ,Cost of capital ,ComputerApplications_MISCELLANEOUS ,Value (economics) ,0202 electrical engineering, electronic engineering, information engineering ,020201 artificial intelligence & image processing ,Credit limit ,business ,ComputingMilieux_MISCELLANEOUS - Abstract
We study joint operational and financing decisions of a cashconstrained manufacturing firm in the presence of bank financing and trade credit, where banks set credit limit based on borrowers repayment histories. Trade credit financing enables the manufacturing firm to build credit history, which affects bank financing availability in the future periods. This can make trade credit valuable, even though it is costly in the current period. We quantify the value of trade credit as a way of securing access to future bank financing and investigate how financing considerations distort the firm’s operational decisions. more...
- Published
- 2017
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6. Modélisation Intégrée du devenir des Pesticides dans les Paysages agricoles (projet MIPP)
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Marc Voltz, Carole Bedos, David Crevoisier, Jean-Christophe Fabre, Benjamin Loubet, Manuel Chataignier, Bankwal, P., Enrique Barriuso, Pierre Benoit, Yves Brunet, Eric Casellas, Patrick Chabrier, Camille Chambon, Cécile Dagès, Jean Paul Douzals, Jean-Louis Drouet, François Lafolie, Laure Mamy, Nicolas Moitrier, Erwan Personne, Valerie Pot, Helene Raynal, Bernadette Ruelle, Anatja Samouëlian, Saudreau, M., Laboratoire d'étude des Interactions Sol - Agrosystème - Hydrosystème (UMR LISAH), Institut de Recherche pour le Développement (IRD)-Institut National de la Recherche Agronomique (INRA)-Centre international d'études supérieures en sciences agronomiques (Montpellier SupAgro)-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), Ecologie fonctionnelle et écotoxicologie des agroécosystèmes (ECOSYS), Institut National de la Recherche Agronomique (INRA)-AgroParisTech, Interactions Sol Plante Atmosphère (UMR ISPA), Institut National de la Recherche Agronomique (INRA)-Ecole Nationale Supérieure des Sciences Agronomiques de Bordeaux-Aquitaine (Bordeaux Sciences Agro), Unité de Mathématiques et Informatique Appliquées de Toulouse (MIAT INRA), Institut National de la Recherche Agronomique (INRA), Information – Technologies – Analyse Environnementale – Procédés Agricoles (UMR ITAP), Institut national de recherche en sciences et technologies pour l'environnement et l'agriculture (IRSTEA)-Institut national d’études supérieures agronomiques de Montpellier (Montpellier SupAgro), Environnement Méditerranéen et Modélisation des Agro-Hydrosystèmes (EMMAH), Institut National de la Recherche Agronomique (INRA)-Avignon Université (AU), AGroécologie, Innovations, teRritoires (AGIR), Institut National de la Recherche Agronomique (INRA)-Institut National Polytechnique (Toulouse) (Toulouse INP), Université Fédérale Toulouse Midi-Pyrénées-Université Fédérale Toulouse Midi-Pyrénées, Laboratoire de Physique et Physiologie Intégratives de l’Arbre en environnement Fluctuant (PIAF), Institut National de la Recherche Agronomique (INRA)-Université Clermont Auvergne [2017-2020] (UCA [2017-2020]), and Université de Toulouse (UT)-Université de Toulouse (UT) more...
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[SDE]Environmental Sciences ,ComputingMilieux_MISCELLANEOUS - Abstract
International audience
- Published
- 2019
7. Wind damage propagation in forests
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David Pivato, Yves Brunet, Sylvain Dupont, Interactions Sol Plante Atmosphère (UMR ISPA), and Institut National de la Recherche Agronomique (INRA)-Ecole Nationale Supérieure des Sciences Agronomiques de Bordeaux-Aquitaine (Bordeaux Sciences Agro) more...
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Canopy ,Atmospheric Science ,Global and Planetary Change ,Meteorology ,[SDE.MCG]Environmental Sciences/Global Changes ,Flow (psychology) ,Forestry ,15. Life on land ,Wind engineering ,damage propagation ,Tree (data structure) ,Bifurcation theory ,forest wind damage ,tree motion ,Breakage ,Wind gust ,wind risk ,Environmental science ,Agronomy and Crop Science ,Wind damage - Abstract
International audience; A key issue for predicting and mitigating the risk of wind damage in forests is to understand the mechanics of damage propagation during windstorms. Until now the acting processes have been poorly understood due to the difficulty of performing measurements in such extreme conditions. Here we use an innovative wind–tree interaction model, which allows for large deflection and tree breakage, to unravel for the first time the mechanisms of damage propagation at forest scale. We find that damage propagation involves two stages. Firstly, initial damage is caused by the impact of strong downward wind gusts. Trees break preferentially at the end of such critical passing sweeps, as the tree motion decelerates. The second stage starts when the damaged areas reach about 5 canopy heights in length and 1 canopy height in width: as the flow accelerates within the damaged areas the mean wind load becomes sufficient to break newly-created edge trees. From this bifurcation point tree damage increases drastically, irrespective of the tree motion state and the type of passing gusts. In addition to demonstrating the possibility of simulating wind damage propagation, these results have considerable potential for improving wind risk models. more...
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- 2015
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8. La chimie et les grandes villes
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Yves Brunet, Stéphane Delalande, Paul-Joël Derian, Valérie Issarny, Romain Lacombe, Christophe Ladaurade, François Michel, Carlos Moreno, Jacques Moussafir, Muriel Olivier, Sandra Rey, Bernard Saunier, Frédéric Thévenet, Jean-Paul Viguier, Yves Brunet, Stéphane Delalande, Paul-Joël Derian, Valérie Issarny, Romain Lacombe, Christophe Ladaurade, François Michel, Carlos Moreno, Jacques Moussafir, Muriel Olivier, Sandra Rey, Bernard Saunier, Frédéric Thévenet, and Jean-Paul Viguier more...
- Subjects
- Environmental chemistry, Urbanization, Cities and towns
- Abstract
Les meilleures projections actuelles font état que 70% au moins de la population mondiale sera citadine en 2050. Comment faire en sorte que ces villes offrent à tous non seulement les services essentiels que sont l'eau, l'énergie et l'assainissement, mais aussi des conditions de vie favorables à leur bienêtre, leur épanouissement et à la santé, c'est-à-dire par exemple prendre les mesures nécessaires pour lutter contre le bruit, la chaleur, la pollution ou pour faciliter la mobilité?Le XXIe siècle sera le siècle des villes, où architecture et urbanisme doivent associer modernité, racines culturelles et diversité des modes de vie. Bien vivre en ville impose des mesures à prendre en compte pour préserver les conditions sanitaires et améliorer le bien-être des habitants. La ville interconnectée optimise la gestion des conditions sanitaires, de la mobilité, de l'usage de l'eau et de l'énergie. La végétation urbaine intervient directement sur la composition atmosphérique et le bilan des pollutions. On sait répondre à la demande croissante d'eau potable malgré la dégradation de la qualité des ressources accessibles. On sait transformer les déchets urbains en ressources énergétiques.La croissance urbaine est une réalité qui nous concerne tous, les défis techniques et organisationnels qu'elle pose sont considérables et le plus souvent transdisciplinaires, mais la chimie y joue toujours un rôle important.Dans cet ouvrage, des réalisations de pointe et des projets avancés sont présentés sur ces questions par les meilleurs spécialistes. L'avenir créé par ces recherches et ces nouvelles technologies sera celui d'un citoyen devenu maître de son environnement, suffisamment informé sur les noeuds de circulation pour choisir son itinéraire, sur les points de pollution du moment pour les éviter, et assez informé pour gérer des consommations de fluides (chauffage, climatisation, électricité, eau, énergie, communication). Grâce aux nombreux recours à la chimie nécessités par ces nouvelles technologies, il deviendra capable d'agir efficacement et non plus de subir un environnement incontrôlable. more...
- Published
- 2017
9. 19. Les échanges d’eau sol-végétation-atmosphère
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Yves Brunet and Andrée Tuzet
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- 2017
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10. 13. Les sols : éléments d'un cycle dynamique
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Marc Voltz and Yves Brunet
- Published
- 2017
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11. Integrated Modelling of pesticide fate in agricultural landscapes
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Marc Voltz, Carole Bedos, Fabre Jc, -., Benjamin Loubet, Mathieu Chataignier, Bankwal P, Enrique Barriuso, Pierre Benoit, Yves Brunet, Eric Casellas, Camille Chambon, David Crevoisier, Cécile Dagès, Jean-Paul Douzals, Drouet Jl, Francois Lafolie, Laure Mamy, Nicolas Moitrier, Erwan Personne, Valerie Pot, Laboratoire d'étude des Interactions Sol - Agrosystème - Hydrosystème (UMR LISAH), Institut de Recherche pour le Développement (IRD)-Institut National de la Recherche Agronomique (INRA)-Centre international d'études supérieures en sciences agronomiques (Montpellier SupAgro)-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), Ecologie fonctionnelle et écotoxicologie des agroécosystèmes (ECOSYS), Institut National de la Recherche Agronomique (INRA)-AgroParisTech, Université Paris Saclay (COmUE), Interactions Sol Plante Atmosphère (UMR ISPA), Institut National de la Recherche Agronomique (INRA)-Ecole Nationale Supérieure des Sciences Agronomiques de Bordeaux-Aquitaine (Bordeaux Sciences Agro), Unité de Mathématiques et Informatique Appliquées de Toulouse (MIAT INRA), Institut National de la Recherche Agronomique (INRA), Institut national de recherche en sciences et technologies pour l'environnement et l'agriculture (IRSTEA), Environnement Méditerranéen et Modélisation des Agro-Hydrosystèmes (EMMAH), and Avignon Université (AU)-Institut National de Recherche pour l’Agriculture, l’Alimentation et l’Environnement (INRAE) more...
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[SDV]Life Sciences [q-bio] ,[SDE]Environmental Sciences ,[INFO]Computer Science [cs] ,[MATH]Mathematics [math] ,ComputingMilieux_MISCELLANEOUS - Abstract
International audience
- Published
- 2017
12. The impact of landscape fragmentation on atmospheric flow: a wind-tunnel study
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Christopher Poette, Yves Brunet, Dale Hughes, Sylvain Dupont, Margi Böhm, Barry Gardiner, John Finnigan, Ian N. Harman, Interactions Sol Plante Atmosphère (ISPA), Institut National de la Recherche Agronomique (INRA)-Ecole Nationale Supérieure des Sciences Agronomiques de Bordeaux-Aquitaine (Bordeaux Sciences Agro), Oceans and Atmosphere, CSIRO, Research School of Biology, Australian National University (ANU), and Interactions Sol Plante Atmosphère (UMR ISPA) more...
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Atmospheric Science ,010504 meteorology & atmospheric sciences ,Meteorology ,[SDV]Life Sciences [q-bio] ,Airflow ,wind tunnel ,Geometry ,Surface finish ,Classification of discontinuities ,boundary layer ,01 natural sciences ,010305 fluids & plasmas ,atmospheric turbulence ,Physics::Fluid Dynamics ,flux atmosphérique ,Fragmentation (mass spectrometry) ,0103 physical sciences ,Shear stress ,fragmented landscape ,turbulence atmosphérique ,0105 earth and related environmental sciences ,Wind tunnel ,edge flow ,turbulent flow ,Turbulence ,15. Life on land ,Turbulence kinetic energy ,Environmental science ,fragmentation du paysage - Abstract
Landscape discontinuities such as forest edges play an important role in determining the characteristics of the atmospheric flow by generating increased turbulence and triggering the formation of coherent tree-scale structures. In a fragmented landscape, consisting of surfaces of different heights and roughness, the multiplicity of edges may lead to complex patterns of flow and turbulence that are potentially difficult to predict. Here, we investigate the effects of different levels of forest fragmentation on the airflow. Five gap spacings (of length approximately 5h, 10h, 15h, 20h, 30h, where h is the canopy height) between forest blocks of length 8.7h, as well as a reference case consisting of a continuous forest after a single edge, were investigated in a wind tunnel. The results reveal a consistent pattern downstream from the first edge of each simulated case, with the streamwise velocity component at tree top increasing and turbulent kinetic energy decreasing as gap size increases, but with overshoots in shear stress and turbulent kinetic energy observed at the forest edges. As the gap spacing increases, the flow appears to change monotonically from a flow over a single edge to a flow over isolated forest blocks. The apparent roughness of the different fragmented configurations also decreases with increasing gap size. No overall enhancement of turbulence is observed at any particular level of fragmentation. more...
- Published
- 2017
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13. Energy Storage: Applications to the Electricity Vector
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Yves Brunet
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Pumped-storage hydroelectricity ,Stand-alone power system ,business.industry ,Energy density ,Environmental science ,Electricity ,business ,Automotive engineering ,Energy storage - Published
- 2013
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14. Effective transverse elastic properties of unidirectional fiber reinforced composites
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T. Kanit, Yves Brunet, Abdellatif Imad, D. Beicha, A. El Moumen, Y. Khelfaoui, Laboratoire de Technologie des Matériaux et Génie des Procédés, Université Abderrahmane Mira [Béjaïa], Laboratoire de Mécanique de Lille - FRE 3723 (LML), Centre National de la Recherche Scientifique (CNRS)-Université de Lille, Sciences et Technologies-Ecole Centrale de Lille-Université de Lille, Université de Lille, Sciences et Technologies, Institut de Recherche Dupuy de Lôme (IRDL), Université de Bretagne Sud (UBS)-Université de Brest (UBO)-École Nationale Supérieure de Techniques Avancées Bretagne (ENSTA Bretagne)-Centre National de la Recherche Scientifique (CNRS), École Nationale Supérieure de Techniques Avancées Bretagne (ENSTA Bretagne), University of Lille, Unité de Mécanique de Lille - ULR 7512 (UML), Université de Lille, Université de Lille, Sciences et Technologies-Ecole Centrale de Lille-Université de Lille-Centre National de la Recherche Scientifique (CNRS), Université de Brest (UBO)-Centre National de la Recherche Scientifique (CNRS)-École Nationale Supérieure de Techniques Avancées Bretagne (ENSTA Bretagne)-Université de Bretagne Sud (UBS), and Université de Lille, Sciences et Technologies-Centrale Lille-Centre National de la Recherche Scientifique (CNRS) more...
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Materials science ,Composite number ,Modulus ,02 engineering and technology ,Fiber-reinforced composite ,Homogenization (chemistry) ,Fiber reinforced composites ,[SPI]Engineering Sciences [physics] ,0203 mechanical engineering ,Random distribution ,General Materials Science ,Composite material ,Elasticity (economics) ,Instrumentation ,ComputingMilieux_MISCELLANEOUS ,Homogenization ,021001 nanoscience & nanotechnology ,Microstructure ,Finite element method ,Elasticity ,Transverse plane ,020303 mechanical engineering & transports ,Mechanics of Materials ,Hexagonal distribution ,Microstructures ,0210 nano-technology - Abstract
International audience; The purpose of this work was to study the influence of microstructure on effective transverse elastic behavior of fiber reinforced composites. Two microstructures were taken into account, hexagonal periodic and random arrangements of fibers. Unlike classical results at low fiber volume fractions and low Young’s modulus contrast between fibers and matrices, results provided by finite elements simulations have shown that microstructure strongly affect the effective properties of composite for both high volume fractions and Young’s modulus contrast. Results were compared to most common analytical models for composites elasticity. more...
- Published
- 2016
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15. Random versus periodic microstructures for elasticity of fibers reinforced composites
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H. Mazouz, A. El Moumen, T. Kanit, Yves Brunet, L. Bouaoune, Université de Batna, Laboratoire de Mécanique de Lille - FRE 3723 (LML), Centre National de la Recherche Scientifique (CNRS)-Université de Lille, Sciences et Technologies-Ecole Centrale de Lille-Université de Lille, Université de Lille, Sciences et Technologies, Institut de Recherche Dupuy de Lôme (IRDL), Université de Bretagne Sud (UBS)-Université de Brest (UBO)-École Nationale Supérieure de Techniques Avancées Bretagne (ENSTA Bretagne)-Centre National de la Recherche Scientifique (CNRS), École Nationale Supérieure de Techniques Avancées Bretagne (ENSTA Bretagne), Université de Lille, Sciences et Technologies-Ecole Centrale de Lille-Université de Lille-Centre National de la Recherche Scientifique (CNRS), Université de Brest (UBO)-Centre National de la Recherche Scientifique (CNRS)-École Nationale Supérieure de Techniques Avancées Bretagne (ENSTA Bretagne)-Université de Bretagne Sud (UBS), Centre National de la Recherche Scientifique (CNRS)-École Nationale Supérieure de Techniques Avancées Bretagne (ENSTA Bretagne)-Université de Brest (UBO)-Université de Bretagne Sud (UBS), and Université de Lille, Sciences et Technologies-Centrale Lille-Centre National de la Recherche Scientifique (CNRS) more...
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Materials science ,Characteristic length ,02 engineering and technology ,Fiber-reinforced composite ,Homogenization (chemistry) ,Industrial and Manufacturing Engineering ,Fiber reinforced composites ,[SPI]Engineering Sciences [physics] ,0203 mechanical engineering ,Elasticity (economics) ,Composite material ,Anisotropy ,Stress concentration ,Mechanical Engineering ,Finite element analysis ,021001 nanoscience & nanotechnology ,Microstructure ,Finite element method ,Particle-reinforcement ,020303 mechanical engineering & transports ,Mechanics of Materials ,Ceramics and Composites ,Microstructures ,0210 nano-technology ,Periodic microstructures - Abstract
International audience; Homogenization of effective elastic properties of fiber reinforced composites frequently supposed periodic arrangement of fibers because such microstructures allow analytical or low computational cost integrations. Hexagonal frame was often preferred than square one which is strongly anisotropic. In practical situations those periodical microstructures are not realistic. Real microstructures are often random or if they are periodic their boundaries don't fit with the periodic scheme. We studied with the help of finite elements samples that exhibit hexagonal arrangement of fibers embedded in a random distribution. Characteristic length scales of hexagonal area were extracted from observation of stress maps. Principal results are a short scale in which bulk and shear stresses become structured. On the other hand we nether reached a size large enough to observe local stress maps similar to those produced by a periodic model. more...
- Published
- 2016
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16. Remobilisation des radionucléides sous forme d’aérosols primaires et secondaires par vent faible à partir de couverts naturels (projet REMORA) : une nouvelle voie de transfert vers l’atmosphère
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Maro, D., Aulagnier, C., Jean-Marc Bonnefond, Yves Brunet, Barbara D'Anna, Frédéric Delmas, M Flaud, P., Floriani, M., Didier Garrigou, Hébert, D., Julien Kammer, Laguionie, P., Eric Lamaud, Morillon, M., Perraudin, E., Pellerin, G., Solier, L., Villenave, E., Institut de Radioprotection et de Sûreté Nucléaire (IRSN), EDF CIDEN, Partenaires INRAE, Interactions Sol Plante Atmosphère (UMR ISPA), Institut National de la Recherche Agronomique (INRA)-Ecole Nationale Supérieure des Sciences Agronomiques de Bordeaux-Aquitaine (Bordeaux Sciences Agro), Institut de recherches sur la catalyse et l'environnement de Lyon (IRCELYON), Université Claude Bernard Lyon 1 (UCBL), Université de Lyon-Université de Lyon-Centre National de la Recherche Scientifique (CNRS)-Institut de Chimie du CNRS (INC), Biologie du fruit et pathologie (BFP), Université Bordeaux Segalen - Bordeaux 2-Institut National de la Recherche Agronomique (INRA)-Université Sciences et Technologies - Bordeaux 1, 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), and Université Paris sciences et lettres (PSL)-Université Paris sciences et lettres (PSL)-Centre National de la Recherche Scientifique (CNRS) more...
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[SDV]Life Sciences [q-bio] ,[SDE]Environmental Sciences ,[SDV.BV]Life Sciences [q-bio]/Vegetal Biology ,ComputingMilieux_MISCELLANEOUS - Abstract
National audience
- Published
- 2016
17. Scientific Committee
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Youssef Fouad, Véronique Carrere, Sabine Chabrillat, Valérie Demarez, Jean Louis Roujean, Roselyne Lacaze, Elizabeth Pattey, Francois Kayitakire, Eric Ceschia, Yves Brunet, David Sheeren, Emmanuelle Vaudour, Samuel Alleaume, Eric Bappel, Samuel Corgne, Damien Arvor, Thibault Catry, Jean-Paul Rudant, Raffaele Gaetano, Eric Mougin, Marie Weiss, Adrien Michez, Sébastien Bauwens, Stéphanie Bonnet, Philippe Lejeune, Thierry Belouard, Nicolas Barbier, Maxime Rejou, Grégoire Vincent, Nicolas Baghdadi, and Mehrez Zribi more...
- Published
- 2016
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18. Comment on 'Critical wind speed at which trees break'
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Hans Christof Spatz, Stephen J. Mitchell, Barry Gardiner, Eric Badel, Pauline Défossez, Meriem Fournier, Axel Albrecht, Frank W. Telewski, Thiéry Constant, Yves Brunet, John Moore, Vivien Bonnesoeur, Bruno Moulia, Mart-Jan Schelhaas, Karl J. Niklas, Sylvain Dupont, Emmanuel de Langre, Bruce C. Nicoll, Forest Research Institute Baden-Wuerttemberg (FVA), Laboratoire de Physique et Physiologie Intégratives de l’Arbre en environnement Fluctuant - Clermont Auvergne (PIAF), Institut National de la Recherche Agronomique (INRA)-Université Clermont Auvergne (UCA), Laboratoire d'Etudes des Ressources Forêt-Bois (LERFoB), Institut National de la Recherche Agronomique (INRA)-AgroParisTech, Interactions Sol Plante Atmosphère (ISPA), Institut National de la Recherche Agronomique (INRA)-Ecole Nationale Supérieure des Sciences Agronomiques de Bordeaux-Aquitaine (Bordeaux Sciences Agro), Ecole Polytechnique, Forest Research, Northern Research Station, Roslin, University of British Columbia (UBC), Scion, Forest Research, Northern Research Station, Cornell University, Alterra [Wageningen] (ESS-CC), Centre for Water and Climate [Wageningen], Albert-Ludwigs-Universität Freiburg, Michigan State University System, Laboratoire de Physique et Physiologie Intégratives de l'Arbre Fruitier et Forestier (PIAF), Institut National de la Recherche Agronomique (INRA)-Université Blaise Pascal - Clermont-Ferrand 2 (UBP), Interactions Sol Plante Atmosphère (UMR ISPA), Cornell University [New York], and AgroParisTech-Institut National de la Recherche Agronomique (INRA) more...
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0106 biological sciences ,0301 basic medicine ,Empirical data ,Astrophysics::High Energy Astrophysical Phenomena ,[SDE.MCG]Environmental Sciences/Global Changes ,Bos- en Landschapsecologie ,Population ,Approx ,01 natural sciences ,Wind speed ,modelling ,03 medical and health sciences ,Tree (descriptive set theory) ,vitesse du vent ,ComputerApplications_MISCELLANEOUS ,Life Science ,Astrophysics::Solar and Stellar Astrophysics ,Forest and Landscape Ecology ,education ,biomécanique de l'arbre ,Vegetatie ,Physics::Atmospheric and Oceanic Physics ,Mathematics ,modélisation ,Discrete mathematics ,education.field_of_study ,Vegetation ,Assertion ,15. Life on land ,030104 developmental biology ,Physics::Space Physics ,Vegetatie, Bos- en Landschapsecologie ,Vegetation, Forest and Landscape Ecology ,Algorithm ,wind speed ,010606 plant biology & botany - Abstract
Virot et al. [E. Virot et al., Phys. Rev. E 93, 023001 (2016)] assert that the critical wind speed at which \ensuremath{\geqslant}50% of all trees in a population break is \ensuremath{\approx}42 m/s, regardless of tree characteristics. We show that empirical data do not support this assertion, and that the assumptions underlying the theory used by Virot et al. are inconsistent with the biomechanics of trees. more...
- Published
- 2016
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19. Turbulent Structures in a Pine Forest with a Deep and Sparse Trunk Space: Stand and Edge Regions
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M. Irvine, Jean-Marc Bonnefond, Yves Brunet, Sylvain Dupont, Eric Lamaud, Écologie fonctionnelle et physique de l'environnement (EPHYSE), and Institut National de la Recherche Agronomique (INRA)
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Canopy ,PLANE MIXING-LAYER FLOW QUADRANT ANALYSIS ,Atmospheric Science ,010504 meteorology & atmospheric sciences ,Meteorology ,[SDE.MCG]Environmental Sciences/Global Changes ,COHERENT EDDY STRUCTURE FOREST CANOPY ,Geometry ,Wake ,01 natural sciences ,MOMENTUM FLUX ,Wind speed ,010305 fluids & plasmas ,TRUNK SPACE ,Wind shear ,0103 physical sciences ,Astrophysics::Solar and Stellar Astrophysics ,0105 earth and related environmental sciences ,Tree canopy ,Turbulence ,WIND SPECTRA ,PIN MARITIME ,15. Life on land ,LARGE-EDDY SIMULATION MARITIME PINE ,TURBULENCE ,Spatial variability ,AUTO-CORRELATION ,Geology ,Large eddy simulation - Abstract
International audience; Forested landscapes often exhibit large spatial variability in vertical and horizontal foliage distributions. This variability may impact canopy-atmosphere ex- changes through its action on the development of turbulent structures. Here we inves- tigate in neutral stratification the turbulent structures encountered in a maritime pine forest characterised by a high, dense foliated layer associated with a deep and sparse trunk space. Both stand and edge regions are considered. In situ measurements and the outputs of large-eddy simulations are used and analysed together. In stand conditions, far from the edge, canopy-top structures appear stronlgy damped by the dense crown layer. Turbulent wind fluctuations within the trunk space, where the momentum flux vanishes, are closely related to these canopy-top structures through pressure diffusion. Consequently, auto-correlation and spectral analyses are not quite appropriate to characterise the vertical scale of coherent structures in this type of canopy, as pressure diffusion enhances the actual scale of structures. At frequencies higher than those associated with canopy-top structures, wind fluctuations related to wake structures developing behind tree stems are observed within the trunk space. They manifest themselves in wind velocity spectra as secondary peaks in the inertial subrange re- gion, confirming the hypothesis of spectral short-cuts in vegetation canopies. In the edge region specific turbulent structures develop just below the crown layer, in addi- tion to canopy-top structures. They are generated by the wind shear induced by the sub-canopy wind jet that forms at the edge. These structures provide a momentum exchange mechanism similar to that observed at the canopy top but in the opposite di- rection and with a lower magnitude. They may develop as in plane mixing-layer flows, with some perturbations induced by canopy-top structures. Wake structures are also observed within the trunk space in the edge region. more...
- Published
- 2012
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20. Microstructure of the solid phase in fluidized beds for non-Stokes regimes
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Qifeng Jiang, Toufik Kanit, Yves Brunet, Laboratoire de Mécanique de Lille - FRE 3723 (LML), Université de Lille, Sciences et Technologies-Ecole Centrale de Lille-Université de Lille-Centre National de la Recherche Scientifique (CNRS), and Université de Lille, Sciences et Technologies-Centrale Lille-Centre National de la Recherche Scientifique (CNRS) more...
- Subjects
Materials science ,Structure factor ,General Physics and Astronomy ,02 engineering and technology ,01 natural sciences ,010305 fluids & plasmas ,Fluidized bed ,Physics::Fluid Dynamics ,symbols.namesake ,Phase (matter) ,0103 physical sciences ,Anisotropy ,Mathematical Physics ,Reynolds number ,Pair distribution function ,Mechanics ,021001 nanoscience & nanotechnology ,Microstructure ,Condensed Matter::Soft Condensed Matter ,Hele-Shaw flow ,Two-dimensional microstructure ,symbols ,Two-phase flow ,0210 nano-technology ,Pair probability - Abstract
International audience; Experiments on two-dimensional fluidized beds of glass beads are presented for two fluids of typical Reynolds numbers of about 1 and a few hundred. The presence of inertial effects leads to the formation of wakes behind the particles and consequently to an anisotropy of the microstructure. The microstructures, studied by video imaging, are characterized by pair probability distribution functions and structure factors. more...
- Published
- 2010
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21. Simultaneous measurements of CO2 and water exchanges over three agroecosystems in South-West France
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Jean-Marc Bonnefond, Eric Lamaud, Yves Brunet, M. Irvine, Patrick Stella, and Denis Loustau
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2. Zero hunger ,0106 biological sciences ,010504 meteorology & atmospheric sciences ,Vapour Pressure Deficit ,Carbon sink ,Primary production ,Vegetation ,15. Life on land ,Carbon sequestration ,01 natural sciences ,Deciduous ,Agronomy ,Environmental science ,Water-use efficiency ,Ecology, Evolution, Behavior and Systematics ,Water use ,010606 plant biology & botany ,0105 earth and related environmental sciences ,Earth-Surface Processes - Abstract
During the last few decades, many studies have been performed to determine water and carbon budgets of broadleaf and deciduous forests, crops and grasslands. However, since most measurements have been made in different regions and at different periods, it is difficult to compare the results directly. In order to evaluate accurately the respective contribution of various agroecosystems to global water and carbon exchanges, it is necessary to compare data obtained in similar climatic and weather conditions. To address this question, we present the results from simultaneous measurements carried out during one year over three typical agroecosystems of the Les Landes region in South-West France:~an agricultural field with maize from 29 May to 18 October, a young (5 year-old) pine forest and a mature (37 year-old) pine forest. All measurements were collected as part of the Regional Experiment component of the CarboEurope-IP project. During most of the year, the agricultural field without vegetation is a source of CO2, but from late June to early September the maize crop becomes a stronger carbon sink than the forests. Over the whole measurement period the three agroecosystems behave as CO2 sinks with carbon storage of about 335, 210 and 160 g C m−2 for the young forest, the mature forest and the agricultural field, respectively. We investigated the influence of climatic conditions on Gross Primary Production (GPP) of the three ecosystems and observed a predominant role of vapour pressure deficit (VPD) for forests and of photosynthetic photon flux density (FPP) for maize. Daily Water Use Efficiencies (WUE) of the three ecosystems were evaluated and expressed as functions of the mean daily vapour pressure deficit (VPD). Similar trends were observed for the two forests, which suggests that for a given species WUE is independent of stand age. The WUE of the maize crop at maturity was also found to depend upon VPD, but it is about twice as large as for the forests, owing to the physiological advantages of C4 species. more...
- Published
- 2009
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22. Évolution de la relation rang-taille dans le système urbain québécois entre 1871 et 1976
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Yves Brunet
- Subjects
Environmental Engineering ,Geography ,Dualism ,Opposition (politics) ,Urban system ,Humanities ,Demography ,Urban structure - Abstract
An analysis of 10 variables caracterising the distribution of the Québec's cities size, permitted identification of 3 distinct phases of evolution of the urban system since 1871. Primatial growth reached a maximum in the 1920s and was followed by a transition-maturation period where, around 1956, the number of centers stabilized at 60. Lognormality was then at a maximum. Since that peak, the metropolisation process induced a new spell of primatial growth. The Quebec urban structure is still markedly unbalanced, the transition from primacy to lognormality is still going on. Its longing could be explained by the fact that in Quebec the "center-periphery" spatial dualism is doubled with an ethno-linguistic dualism. Without the french-english opposition one can think that the transition period would have resolved rapidly with the development of non-metropolitan industrial complexes. more...
- Published
- 2009
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23. Influence of foliar density profile on canopy flow: A large-eddy simulation study
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Yves Brunet, Sylvain Dupont, Écologie fonctionnelle et physique de l'environnement (EPHYSE), and Institut National de la Recherche Agronomique (INRA)
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Length scale ,Canopy ,Atmospheric Science ,010504 meteorology & atmospheric sciences ,Meteorology ,VEGETATION CANOPY ,TURBULENT FLOW ,Biometeorology ,Atmospheric sciences ,01 natural sciences ,Wind speed ,[SDV.SA.SF]Life Sciences [q-bio]/Agricultural sciences/Silviculture, forestry ,COHERENT STRUCTURES ,MIXING-LAYER ANALOGY ,Lagrangian coherent structures ,0105 earth and related environmental sciences ,040101 forestry ,Global and Planetary Change ,LARGE-EDDY SIMULATION ,WAVELET TRANSFORM ,FOREST MORPHOLOGY ,Turbulence ,Forestry ,04 agricultural and veterinary sciences ,15. Life on land ,Vegetation canopy ,0401 agriculture, forestry, and fisheries ,Agronomy and Crop Science ,Geology ,Large eddy simulation - Abstract
The Advanced Regional Prediction System (ARPS) has been modified so as to simulate turbulent flow at very fine scale within and above vegetation canopies using a large-eddy simulation (LES) approach. It is first shown that this new version of ARPS is able to reproduce accurately all essential features of turbulent flow over homogeneous canopies. A sensitivity study of the flow to the morphology of the canopy, i.e. the density and vertical leaf-area (LAI) distribution, is then performed numerically over three types of canopies with five levels of leaf-area index, from 1 to 5. This study confirms the universal characteristics of turbulent flow over vegetation canopies, as previously observed from wind-tunnel and in situ experiments. It shows that the typical features of canopy flow become more pronounced as canopy density increases, and quantifies the extent to which differences in canopy morphology can explain the experimental variability observed between canopies. This variability in turbulent characteristics is mostly visible in the subcanopy space, and depends significantly on the density of the upper foliated layers. The mean longitudinal separation Λ w between adjacent coherent structures has also been computed for each canopy using the wavelet transform and approximating the convection velocity of coherent structures as 1.8 times the average wind velocity at canopy top. Except for the sparsest canopies, the analogy between the atmospheric flow near the top of a vegetation canopy and a plane mixing layer is well verified: Λ w is directly related to the shear length scale L s = U ( h ) / U ′ ( h ) , where h is canopy height, U mean velocity and U ′ is the vertical gradient d U / d z , in a way close to the prediction Λ w / h = 8.1 L s / h . more...
- Published
- 2008
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24. Impact of forest edge shape on tree stability: a large-eddy simulation study
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Yves Brunet, Sylvain Dupont, Écologie fonctionnelle et physique de l'environnement (EPHYSE), and Institut National de la Recherche Agronomique (INRA)
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0106 biological sciences ,010504 meteorology & atmospheric sciences ,Turbulence ,Forestry ,Geometry ,15. Life on land ,Edge (geometry) ,Wake ,01 natural sciences ,Wind engineering ,Physics::Geophysics ,Tree (data structure) ,[SDV.SA.SF]Life Sciences [q-bio]/Agricultural sciences/Silviculture, forestry ,Bending moment ,Physics::Atmospheric and Oceanic Physics ,Geology ,010606 plant biology & botany ,0105 earth and related environmental sciences ,Wind tunnel ,Large eddy simulation - Abstract
International audience; As forest edges are often associated with wind damage, it may be of interest to modify the edge region in order to reduce wind-induced risks. To this purpose, this study investigates tree vulnerability to wind load downwind from leading edges designed with various treatments: sharp, tapered, sparse, dense, tall and small edges. Using a large-eddy simulation flow model, instantaneous wind and turbulence fields are simulated on either side of each edge. These fields are then used to compute mean and extreme tree bending moments as well as their ratio, the gust factor. The behaviour of these variables downwind from the edge agrees well with previous wind tunnel measurements. The gust factor increases at some distance behind the edge, due to the development of coherent eddy structures generated at the canopy-air interface. Unlike wind gusts in the vicinity of the edge, these structures penetrate deep within the canopy through sweep motions. Tree vulnerability is slightly reduced downwind from tapered, sparse and small edges and enhanced downwind from dense ones. Behind tall edges, the gust factor is reduced in the edge region but enhanced further downstream due to the interaction of the canopy with the wake of the edge treatment. more...
- Published
- 2008
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25. Edge Flow and Canopy Structure: A Large-Eddy Simulation Study
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Yves Brunet, Sylvain Dupont, Écologie fonctionnelle et physique de l'environnement (EPHYSE), and Institut National de la Recherche Agronomique (INRA)
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Canopy ,Atmospheric Science ,Leading edge ,010504 meteorology & atmospheric sciences ,Meteorology ,Planetary boundary layer ,[SDV]Life Sciences [q-bio] ,Flow (psychology) ,VEGETATION CANOPY ,TURBULENT FLOW ,WIND DAMAGE ,Atmospheric sciences ,DEGAT DU VENT ,01 natural sciences ,Physics::Geophysics ,010305 fluids & plasmas ,Physics::Fluid Dynamics ,FOREST EDGE ,0103 physical sciences ,Astrophysics::Solar and Stellar Astrophysics ,0105 earth and related environmental sciences ,Jet (fluid) ,LARGE-EDDY SIMULATION ,FOREST MORPHOLOGY ,Turbulence ,CANOPEE ,15. Life on land ,ECOULEMENT TURBULENT ,Skewness ,[SDE]Environmental Sciences ,Geology ,Large eddy simulation - Abstract
International audience; Sharp heterogeneities in forest structure, such as edges, are often responsible for wind damage. In order to better understand the behaviour of turbulent flow through canopy edges, large-eddy simulations (LES) have been performed at very fine scale (2 m) within and above heterogeneous vegetation canopies. A modified version of the Advanced Regional Prediction System (ARPS), previously validated in homogeneous conditions against field and wind-tunnel measurements, has been used for this purpose. Here it is validated in a simple forest-clearing-forest configuration. The model is shown to be able to reproduce accurately the main features observed in turbulent edge flow, especially the "enhanced gust zone" (EGZ) present around the canopy top at a few canopy heights downwind from the edge, and the turbulent region that develops further downstream. The EGZ is characterized by a peak in streamwise velocity skewness, which reflects the presence of intense intermittent wind gusts. A sensitivity study of the edge flow to the forest morphology shows that with increasing canopy density the flow adjusts faster and turbulent features such as the EGZ become more marked. When the canopy is characterized by a sparse trunk space the length of the adjustment region increases significantly due to the formation of a sub-canopy wind jet from the leading edge. It is shown that the position and magnitude of the EGZ are related to the mean upward motion formed around canopy top behind the leading edge, caused by the deceleration in the sub-canopy. Indeed, this mean upward motion advects low turbulence levels from the bottom of the canopy; this emphasises the passage of sudden strong wind gusts from the clearing, thereby increasing the skewness in streamwise velocity as compared with locations further downstream where ambient turbulence is stronger. more...
- Published
- 2007
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26. A Fine-Scale k−ε Model for Atmospheric Flow over Heterogeneous Landscapes
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H. Foudhil, Jean-Paul Caltagirone, and Yves Brunet
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Meteorology ,Computer simulation ,Scale (ratio) ,Turbulence ,Planetary boundary layer ,Airflow ,Flow (psychology) ,Mechanics ,Atmospheric model ,Physics::Fluid Dynamics ,Turbulence kinetic energy ,Environmental Chemistry ,Environmental science ,Water Science and Technology - Abstract
A multi-purpose model for small-scale atmospheric flows over heterogeneous landscapes is being developed. The aim of this research is to build a tool able to predict the dynamical (wind, turbulence) and diffusive (gases, particles) fields over landscapes characterised by heterogeneous plant cover. In its present stage of development the model is based on the numerical integration of neutral atmospheric flow equations, using an energy-dissipation closure scheme and over a domain that may include vegetation layers. Three validation cases of the model are presented: (i) response of the airflow to a change in surface roughness; (ii) airflow within and above a horizontally homogeneous plant canopy; (iii) airflow over two complex forest-to-clearing and clearing-to-forest transitions. All simulations provide results in good agreement with the experimental data, except for turbulent kinetic energy just after a clearing-to-forest transition. This result is not surprising for a statistical k−e model in a flow region characterised by strong distorsion and intermittent turbulence. However the overall good performance of the model is promising for environmental research at fine scales over heterogeneous landscapes. more...
- Published
- 2005
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27. Transpiration and CO2 fluxes of a pine forest: modelling the undergrowth effect
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Paul Berbigier, André Granier, Vincent Rivalland, Yves Brunet, and J.-Ch. Calvet
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Canopy ,Atmospheric Science ,Tree canopy ,010504 meteorology & atmospheric sciences ,0207 environmental engineering ,Geology ,Astronomy and Astrophysics ,02 engineering and technology ,Understory ,Vegetation ,15. Life on land ,Atmospheric sciences ,01 natural sciences ,Water balance ,13. Climate action ,Space and Planetary Science ,Evapotranspiration ,Earth and Planetary Sciences (miscellaneous) ,Environmental science ,020701 environmental engineering ,0105 earth and related environmental sciences ,Undergrowth ,Transpiration - Abstract
A modelling study is performed in order to quantify the relative effect of allowing for the physiological properties of an undergrowth grass sward on total canopy water and carbon fluxes of the Le-Bray forest (Les-Landes, South-western France). The Le-Bray forest consists of maritime pine and an herbaceous undergrowth (purple moor-grass), which is characterised by a low stomatal control of transpiration, in contrast to maritime pine. A CO2-responsive land surface model is used that includes responses of woody and herbaceous species to water stress. An attempt is made to represent the properties of the undergrowth vegetation in the land surface model Interactions between Soil, Biosphere, and Atmosphere, CO2-responsive, ISBA-A-gs. The new adjustment allows for a fairly different environmental response between the forest canopy and the understory in a simple manner. The model's simulations are compared with long term (1997 and 1998) micro-meteorological measurements over the Le-Bray site. The fluxes of energy, water and CO2, are simulated with and without the improved representation of the undergrowth vegetation, and the two simulations are compared with the observations. Accounting for the undergrowth permits one to improve the model's scores. A simple sensitivity experiment shows the behaviour of the model in response to climate change conditions, and the understory effect on the water balance and carbon storage of the forest. Accounting for the distinct characteristics of the undergrowth has a substantial and positive effect on the model accuracy and leads to a different response to climate change scenarios. more...
- Published
- 2005
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28. MuSICA , a CO2 , water and energy multilayer, multileaf pine forest model: evaluation from hourly to yearly time scales and sensitivity analysis
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Denis Loustau, Sylvain Delzon, Paul Berbigier, Yves Brunet, and Jérôme Ogée
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0106 biological sciences ,Hydrology ,Canopy ,Global and Planetary Change ,010504 meteorology & atmospheric sciences ,Ecology ,Moisture ,Understory ,Vegetation ,15. Life on land ,Sensible heat ,Atmospheric sciences ,01 natural sciences ,FluxNet ,13. Climate action ,Soil water ,Litter ,Environmental Chemistry ,Environmental science ,010606 plant biology & botany ,0105 earth and related environmental sciences ,General Environmental Science - Abstract
The current emphasis on global climate studies has led the scientific community to set up a number of sites for measuring long-term biospheric fluxes, and to develop a wide range of biosphere–atmosphere exchange models. This paper presents a new model of this type, which has been developed for a pine forest canopy. In most coniferous species the canopy layer is well separated from the understorey and several cohorts of needles coexist. It was therefore found necessary to distinguish several vegetation layers and, in each layer, several leaf classes defined not only by their light regime and wetness status but also by their age. This model, named MuSICA, is a multilayer, multileaf process-based model. Each submodel is first independently parameterized using data collected at a EUROFLUX site near Bordeaux (Southwestern France). Particular care is brought to identify the seasonal variations in the various physiological parameters. The full model is then evaluated using a two-year long data set, split up into 12 day-type classes defined by the season, the weather type and the soil water status. Beyond the good overall agreement obtained between measured and modelled values at various time scales, several points of further improvement are identified. They concern the seasonal variations in the stomatal response of needles and the soil/litter respiration, as well as their interaction with soil or litter moisture. A sensitivity analysis to some of the model features (in-canopy turbulent transfer scheme, leaf age classes, water retention, distinction between shaded and sunlit leaves, number of layers) is finally performed in order to evaluate whether significant simplifications can be brought to such a model with little loss in its predictive quality. The distinction between several leaf classes is crucial if one is to compute biospheric fluxes accurately. It is also evidenced that accounting for in-canopy turbulent transfer leads to better estimates of the sensible heat flux. more...
- Published
- 2003
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29. A forest floor model for heat and moisture including a litter layer
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Jérôme Ogée, Yves Brunet, Unité de bioclimatologie, and Institut National de la Recherche Agronomique (INRA)
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Canopy ,soil temperature ,010504 meteorology & atmospheric sciences ,[SDV]Life Sciences [q-bio] ,0207 environmental engineering ,force-restore method ,02 engineering and technology ,Atmospheric sciences ,01 natural sciences ,evaporation ,020701 environmental engineering ,Water content ,0105 earth and related environmental sciences ,Water Science and Technology ,Forest floor ,Hydrology ,Moisture ,Mathematical model ,EUROFLUX ,Vegetation ,15. Life on land ,[SDE]Environmental Sciences ,Soil water ,Litter ,Environmental science ,soil moisture - Abstract
International audience; Forest soils are often covered with a litter that influences the rate of mass and energy transfer between the soil and the air above, thereby modifying the temperature and moisture fields in the soil. The presence of a litter should therefore be accounted for in forest SVAT models, especially when long-term simulations are to be performed. A heat and moisture litter model has been developed by adding two dynamical equations to a force-restore type soil model. The experimental data used for the model validation was collected in a pine forest canopy in the South-West of France, that was part of the Euroflux network. The model is tested and validated over a two-year period. It is shown to provide a fairly good simulation of soil and litter moisture, soil and litter temperature and turbulent fluxes measured above the forest floor. It is also shown that simulations without the litter layer are unable to reproduce all these variables simultaneously. We then perform a sensitivity analysis to the parameters whose values are either uncertain or likely to be variable in time and space, such as the litter thickness, the rainfall fraction intercepted by the litter or the maximum value of the surface resistance. A threshold value of the litter moisture used in the surface resistance parameterisation turns out to be the most critical parameter. Further work is needed to investigate the possible relationships between the various parameters describing the litter, but the present litter model can already be used in combination with other forest SVAT models. more...
- Published
- 2002
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30. Wind flow dynamics over a vineyard
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Yves Brunet, Carole Sinfort, Ali Chahine, Sylvain Dupont, Interactions Sol Plante Atmosphère (ISPA), Institut National de la Recherche Agronomique (INRA)-Ecole Nationale Supérieure des Sciences Agronomiques de Bordeaux-Aquitaine (Bordeaux Sciences Agro), Institut national d’études supérieures agronomiques de Montpellier (Montpellier SupAgro), Interactions Sol Plante Atmosphère (UMR ISPA), and Institut national d'enseignement supérieur pour l'agriculture, l'alimentation et l'environnement (Institut Agro) more...
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Atmospheric Science ,010504 meteorology & atmospheric sciences ,Aspect ratio ,Meteorology ,Astrophysics::High Energy Astrophysical Phenomena ,[SDE.MCG]Environmental Sciences/Global Changes ,Stratification (water) ,Computer Science::Computational Geometry ,Atmospheric sciences ,Row canopy ,Vineyard ,01 natural sciences ,010305 fluids & plasmas ,Turbulent flow ,Physics::Fluid Dynamics ,Large-eddy simulation ,0103 physical sciences ,Astrophysics::Solar and Stellar Astrophysics ,Mean flow ,Physics::Atmospheric and Oceanic Physics ,0105 earth and related environmental sciences ,écoulement d'air turbulent ,Turbulence ,Wind flow ,15. Life on land ,Wind direction ,structure turbulente ,grapevine ,Roughness length ,Turbulence kinetic energy ,Physics::Space Physics ,Environmental science ,Spatial variability ,vigne - Abstract
Wind-flow dynamics has been extensively studied over horizontally uniform canopies, but agricultural plantations structured in rows such as vineyards have received less attention. Here, the wind flow over a vineyard is studied in neutral stratification from both large-eddy simulation (LES) and in situ measurements. The impact of row structure on the wind dynamics is investigated over a range of wind directions from cross-row to down-row, and a typical range of row aspect ratio (row separation/height ratio). It is shown that the mean flow over a vineyard is similar to that observed in uniform canopies, especially for wind directions from cross-row to diagonal. For down-row winds, the mean flow exhibits noticeable spatial variability across each elementary row-gap pattern, as the wind is channeled in the inter-row. This spatial variability increases with the aspect ratio. With down-row winds the turbulent structures are also more intermittent and generate larger turbulent kinetic energy and momentum flux. The displacement height and roughness length of the vineyard vary with the aspect ratio in a way similar to their variation with canopy density in uniform canopies. Both parameters take smaller values in down-row wind flow, for which the canopy appears more open. The analysis of velocity spectra and autocorrelation functions shows that vineyard canopies share similar features to uniform canopies in terms of turbulent coherent structures, with only minor changes with wind direction. more...
- Published
- 2014
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31. A simple tree swaying model for forest motion in windstorm conditions
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David Pivato, Yves Brunet, Sylvain Dupont, Écologie fonctionnelle et physique de l'environnement (EPHYSE), and Institut National de la Recherche Agronomique (INRA)
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Ecology ,Physiology ,Turbulence ,Modal analysis ,[SDE.MCG]Environmental Sciences/Global Changes ,Forestry ,Plant Science ,Mechanics ,Tree motion ,15. Life on land ,Curvature ,Wind speed ,Wind engineering ,Turbulent flow ,Tree (data structure) ,Drag ,Windstorm ,Physics::Space Physics ,Fluid–structure interaction ,Decision tree model ,ComputingMilieux_MISCELLANEOUS ,Mathematics ,Wind damage - Abstract
A simple tree swaying model, valid for windstorm conditions, has been developed for the purpose of simulating the effect of strong wind on the vulnerability of heterogeneous forest canopies. In this model the tree is represented as a flexible cantilever beam whose motion, induced by turbulent winds, is solved through a modal analysis. The geometric nonlinearities related to the tree curvature are accounted for through the formulation of the wind drag force. Furthermore, a breakage condition is considered at very large deflections. A variety of case studies is used to evaluate the present model. As compared to field data collected on three different tree species, and to the outputs of mechanistic models of wind damage, it appears to be able to predict accurately large tree deflections as well as tree breakage, using wind velocity at tree top as a forcing function. The instantaneous response of the modelled tree to a turbulent wind load shows very good agreement with a more complex tree model. The simplicity of the present model and its low computational time make it well adapted to future use in large-eddy simulation airflow models, aimed at simulating the complete interaction between turbulent wind fields and tree motion in fragmented forests. more...
- Published
- 2014
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32. Evaluation de la fraction volumique locale de la phase solide dans un écoulement diphasique
- Author
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Alain Merlen, Corinne Bounhoure, and Yves Brunet
- Subjects
Geotechnical Engineering and Engineering Geology - Abstract
Resume Les mesures des fractions volumiques locales sont rares en ecoulements diphasiques fluide-particules. En general, la concentration est supposee spatialement homogene dans les experiences fondamentales concernant les ecoulements sedimentaires. Ceci est loin d'etre verifie hors du regime de Stokes, en particulier au voisinage de parois. Cette note presente deux methodes qui, moyennant quelques restrictions, donnent acces a cette fraction volumique dans un ecoulement diphasique tridimensionnel. more...
- Published
- 2001
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33. A long-term study of soil heat flux under a forest canopy
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Yves Brunet, Paul Berbigier, Eric Lamaud, Jérôme Ogée, Jean-Marc Bonnefond, Unité de bioclimatologie, and Institut National de la Recherche Agronomique (INRA)
- Subjects
Atmospheric Science ,010504 meteorology & atmospheric sciences ,[SDE.MCG]Environmental Sciences/Global Changes ,Energy balance ,Sensible heat ,Thermal energy storage ,Atmospheric sciences ,01 natural sciences ,soil heat flux ,understorey ,Soil thermal properties ,Thermal conductivity ,Water content ,0105 earth and related environmental sciences ,Hydrology ,Global and Planetary Change ,Forestry ,04 agricultural and veterinary sciences ,15. Life on land ,long-term energy budget ,forest canopy ,Heat flux ,13. Climate action ,Soil water ,040103 agronomy & agriculture ,0401 agriculture, forestry, and fisheries ,Environmental science ,Agronomy and Crop Science - Abstract
International programmes such as EUROFLUX focus on the analysis of long-term fluxes and energy budgets in the biosphere. Reliable estimates of hourly energy budgets require an accurate estimation of soil heat flux, that is often non-negligible even in a forest, and can be predominant during the night. Over long periods of time such as one to several months, its contribution can also be significant. The present work has been carried out to get good estimates of the soil heat flux in a maritime pine stand in the southwest of France, one of the 15 EUROFLUX sites. Using a whole year’s worth of data, soil heat flux was estimated by a two-step version of the null-alignment method using soil temperature, water content and bulk density measurements between the soil surface and a depth of 1 m. A data subset was firstly used to estimate and model the soil thermal conductivity at various depths. The full data set was then used with the modelled conductivity to estimate heat storage between the surface and a reference depth, and calculate the heat flux at the soil surface. Throughout the investigated year and at a 30 min time scale, the soil heat flux represents 5‐10% of the incident net radiation, i.e. 30‐50% of the net radiation over the understorey. Cumulative values from September 1997 to March 1998 reach a maximum of 70 MJ m 2 , which represents nearly 50% of the cumulative values of transmitted net radiation (140 MJ m 2 ) over the same period. These estimates of soil heat flux allowed the energy budgets of the whole stand and the understorey to be closed, and showed that the storage terms are significant not only at a 30 min time scale but also at longer time scales (a few weeks). An attempt was finally made to model soil heat flux from meteorological data, which has rarely been done for a forest soil and over a long-term data set. In most of the existing models, soil heat flux is taken as a fraction of net radiation or sensible heat flux. Here, the litter acts as a mulch at the soil surface so that the only significant terms of the energy balance at this level are soil heat flux, transmitted net radiation and turbulent sensible heat flux. Soil heat flux is shown to be a linear combination of (1) net radiation above the understorey with a clear dependence of the coefficient on the soil cover fraction, and (2) the difference between the air and litter temperatures, with little influence of soil water content or wind speed on the coefficient. © 2001 Elsevier Science B.V. All rights reserved. more...
- Published
- 2001
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34. Structures instationnaires formées par la rencontre d'un jet et d'un écoulement transverse
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Yves Brunet and Jean-Noël Blanchard
- Subjects
General Physics and Astronomy ,General Chemistry - Abstract
Resume La rencontre d'un jet et d'un ecoulement perpendiculaire engendre des structures tourbillonnaires instationnaires, a la frontiere du jet. Cette note decrit, a partir de visualisations quantitatives, l'evolution de ces structures. Une des evolutions possibles est particulierement detaillee: le processus d'appariement entre deux tourbillons consecutifs. more...
- Published
- 2000
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35. Energy Storage
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Yves Brunet
- Subjects
Materials science ,Waste management ,Energy storage - Published
- 2013
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36. Wind risk in forest growth, value and management models: the FOR-WIND project
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Meriem Fournier, Barry Gardiner, Vivien Bonnesoeur, Bravo, F., Yves Brunet, Marielle Brunette, Francis Colin, Thiery Constant, Frederic Danjon, Francois Rouault de Coligny, Pauline Defossez, Sylvain Dupont, Mathieu Fortin, Thierry Fourcaud, Kana Kamimura, Myriam Legay, Rubén Manso, Céline Meredieu, Bruno Moulia, Olivar, J., Christopher Poette, P Renaud, J., Anne Stenger-Letheux, Holger Wernsdorfer, Ming Yang, Laboratoire d'Etudes des Ressources Forêt-Bois (LERFoB), AgroParisTech-Institut National de la Recherche Agronomique (INRA), Écologie fonctionnelle et physique de l'environnement (EPHYSE), Institut National de la Recherche Agronomique (INRA), Laboratoire d'Economie Forestière (LEF), Biodiversité, Gènes & Communautés (BioGeCo), Institut National de la Recherche Agronomique (INRA)-Université de Bordeaux (UB), Botanique et Modélisation de l'Architecture des Plantes et des Végétations (UMR AMAP), Centre National de la Recherche Scientifique (CNRS)-Université de Montpellier (UM)-Institut National de la Recherche Agronomique (INRA)-Centre de Coopération Internationale en Recherche Agronomique pour le Développement (Cirad)-Institut de Recherche pour le Développement (IRD [France-Sud]), Laboratoire de Physique et Physiologie Intégratives de l'Arbre Fruitier et Forestier (PIAF), Institut National de la Recherche Agronomique (INRA)-Université Blaise Pascal - Clermont-Ferrand 2 (UBP), European Forest Institute (EFI). INT., Institut National de la Recherche Agronomique (INRA)-AgroParisTech, Écologie fonctionnelle et physique de l'environnement (EPHYSE - UR1263), Biodiversité, Gènes et Communautés, and Centre de Coopération Internationale en Recherche Agronomique pour le Développement (Cirad)-Institut National de la Recherche Agronomique (INRA)-Université de Montpellier (UM)-Centre National de la Recherche Scientifique (CNRS)-Institut de Recherche pour le Développement (IRD [France-Sud]) more...
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[SDE.MCG]Environmental Sciences/Global Changes ,vent ,gestion forestière ,Milieux et Changements globaux ,modèle de croissance - Abstract
absent
- Published
- 2013
37. Ontologie et temporalité. Esquisse d'une interprétation intégrale de Sein und ZeitJean Greisch Collection «Épiméthée» Paris, Presses Universitaires de France, 1994, VI 522 p
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Yves Brunet
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Philosophy - Published
- 1996
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38. A wind tunnel study of air flow in waving wheat: Two-point velocity statistics
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Roger H. Shaw, John Finnigan, Yves Brunet, M. R. Raupach, University of California [Davis] (UC Davis), University of California, Unité de bioclimatologie, Institut National de la Recherche Agronomique (INRA), and Commonwealth Scientific and Industrial Research Organisation [Canberra] (CSIRO) more...
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Atmospheric Science ,Drag coefficient ,010504 meteorology & atmospheric sciences ,Planetary boundary layer ,Turbulence ,[SDV]Life Sciences [q-bio] ,01 natural sciences ,Wind speed ,010305 fluids & plasmas ,Boundary layer ,0103 physical sciences ,Turbulence kinetic energy ,Statistics ,Astrophysics::Solar and Stellar Astrophysics ,Shear velocity ,Geology ,0105 earth and related environmental sciences ,Wind tunnel - Abstract
International audience; Two-point, space-time correlations of streamwise and vertical velocity were obtained from a wind tunnel simulation of an atmospheric surface layer with an underlying model wheat canopy constructed of flexible nylon stalks. Velocity data extend from 1/6 canopy height to several canopy heights, with in excess of 2000 three-dimensional vector separations of the two x-wire probes. Isocorrelation contours over anx, z slice show the streamwise velocity autocorrelation to be roughly circular, such that vertical velocities at the same horizontal position but different heights are closely in phase. Cross-correlations between the two velocity components reflect this difference to some extent. Lateral displacements of the probes revealed side lobes with correlations of reversed sign but we cannot positively link this pattern to particular vorticular structures. Integral length scales obtained directly from the spatial correlations match similar scales deduced from single-point time series with Taylor's hypothesis at 2 to 3 times the canopy height but greatly exceed such scales at lower levels, particularly within the wheat. We conclude that the reversed sign lateral lobes are important components of the correlation field and that an integral length scale for the lateral direction must be defined such that they are included. Convective velocities obtained from the time lag to optimally restore correlation lost by physical separation of the probes change only slowly with height and greatly exceed the mean wind velocity within and immediately above the canopy. Thus, mean wind velocity is not a suitable proxy for convective velocity in the application of Taylor's hypothesis in this situation. The ratio of vertical to longitudinal convective velocity for the streawise velocity signal yields a downwind tilt angle of about 39° which is probably a better estimate of the slope of the dominant fluid motions than the tilt of the major axis of the isocorrellation contours mentioned previously. more...
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- 1995
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39. An experimental study of angular effects on surface temperature for various plant canopies and bare soils
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Yann Kerr, Jean-Pierre Lagouarde, Yves Brunet, Unité de bioclimatologie, Institut National de la Recherche Agronomique (INRA), Centre d'études spatiales de la biosphère (CESBIO), Centre National de la Recherche Scientifique (CNRS)-Institut de Recherche pour le Développement (IRD)-Institut National de Recherche pour l’Agriculture, l’Alimentation et l’Environnement (INRAE)-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), and 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) more...
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Atmospheric Science ,Global and Planetary Change ,Brightness ,Materials science ,Radiometer ,010504 meteorology & atmospheric sciences ,[SDV]Life Sciences [q-bio] ,Forestry ,04 agricultural and veterinary sciences ,01 natural sciences ,Computational physics ,Azimuth ,Brightness temperature ,040103 agronomy & agriculture ,Emissivity ,Radiative transfer ,Nadir ,0401 agriculture, forestry, and fisheries ,Radiometry ,Agronomy and Crop Science ,0105 earth and related environmental sciences ,Remote sensing - Abstract
Workshop on Thermal Remote Sensing of the Energy and Water Balance Over Vegetation in Conjunction with Other Sensors, La-Londe-des-Maures, 20-24 septembre 1993; International audience; Surface temperature is a key parameter for assessing fluxes at the surface-atmosphere interface. Proper estimation of radiative surface temperature requires corrections for perturbating factors such as atmospheric contributions and angular effects. Several models have been derived to address angular effects, but relevant data for validating such models is still scarce. This paper describes a field experiment dedicated to collecting angular measurements of brightness surface temperature over several types of surfaces (bare soils with different roughnesses, corn, grass, alfalfa), using a unique measurement protocol with simultaneous temperature readings at two angles. For each surface zenithal and azimuthal angular effects are quantified. In some cases (unstressed, fully-covering alfalfa) the difference between oblique and vertical brightness temperatures is within ±0.5 K. Over stressed corn the temperature measured at angles of ±60° is about 4 K less than the nadir looking temperature, but it is 3.5 K higher over a ploughed bare soil, when the inclined radiometer faces the sunlit side of the furrows. Over a bare smooth soil the observed angular variations are shown to be compatible with those due to possible angular variations in emissivity. All the results are discussed in terms of surface geometry and microclimatic conditions, and compared to previous studies. Implications are deduced for the interpretation of satellite measurements of surface temperature. more...
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- 1995
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40. Energy Storage
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Yves Brunet and Yves Brunet
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- Electric power supplies to apparatus, Energy storage
- Abstract
Energy storage examines different applications such as electric power generation, transmission and distribution systems, pulsed systems, transportation, buildings and mobile applications. For each of these applications, proper energy storage technologies are foreseen, with their advantages, disadvantages and limits. As electricity cannot be stored cheaply in large quantities, energy has to be stored in another form (chemical, thermal, electromagnetic, mechanical) and then converted back into electric power and/or energy using conversion systems. Most of the storage technologies are examined: batteries, hydrogen, super capacitors, SMES, flywheels, CAES, thermal storage and hydraulic gravitational storage. more...
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- 2011
41. Surface renewal analysis: a new method to obtain scalar fluxes
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Tomonori Watanabe, Yves Brunet, Kyaw Tha Paw U, Hong-Bing Su, Jie Qiu, UC Davis Biometeorology Group, University of California [Davis] (UC Davis), University of California-University of California, University of California, Unité de bioclimatologie, and Institut National de la Recherche Agronomique (INRA) more...
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Canopy ,Atmospheric Science ,Global and Planetary Change ,Tree canopy ,010504 meteorology & atmospheric sciences ,Meteorology ,Turbulence ,Scalar (mathematics) ,0207 environmental engineering ,Forestry ,02 engineering and technology ,15. Life on land ,Atmospheric sciences ,01 natural sciences ,Wind speed ,Stability conditions ,[SDV.SA.SF]Life Sciences [q-bio]/Agricultural sciences/Silviculture, forestry ,Air temperature ,Environmental science ,Renewal theory ,020701 environmental engineering ,Agronomy and Crop Science ,0105 earth and related environmental sciences - Abstract
International audience; A new method for estimating scalar fluxes, called surface renewal analysis, was developed and successfully tested with air temperature data from a maize crop, an orchard, and a forest canopy. The method employs the scalar trace and is based on the concept of turbulent coherent structures causing most of the scalar fluxes. It was generally more accurate than other scalar based methods such as the Tillman variance method, and can be applied to data gathered under stable stability conditions. Filtering the temperature trace, based on the wind speed at the canopy height, resulted in more accurate surface renewal estimates than when raw 10 Hz data were used. more...
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- 1995
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42. Long-distance pollen flow in large fragmented landscapes
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X. Foueillassar, A. Audran, Sylvia Dayau, J. Escobar, D. Garrigou, J.‐P. Pinty, P. Tulet, S. Dupont, Dominique Guyon, Yves Brunet, C. Lac, S. Delage, Écologie fonctionnelle et physique de l'environnement (EPHYSE), Institut National de la Recherche Agronomique (INRA), 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), Équipe Troposphère, 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 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, Institut national des sciences de l'Univers (INSU - CNRS)-Météo France-Centre National de la Recherche Scientifique (CNRS), Bontoux SA, Arvalis, ARVALIS - Institut du végétal [Paris], Yves Bertheau, INRA, Météo France et le laboratoire d'aérologie de Toulouse, European Project, Écologie fonctionnelle et physique de l'environnement (EPHYSE - UR1263), Laboratoire d'aérologie (LA), Université Fédérale Toulouse Midi-Pyrénées-Université Fédérale Toulouse Midi-Pyrénées-Université Toulouse III - Paul Sabatier (UT3), 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)-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 -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) more...
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010504 meteorology & atmospheric sciences ,Pollination ,Planetary boundary layer ,Flow (psychology) ,long-distance dispersal ,[SDU.STU.ME]Sciences of the Universe [physics]/Earth Sciences/Meteorology ,Atmospheric sciences ,medicine.disease_cause ,maize ,01 natural sciences ,atmospheric turbulence ,[SPI.MECA.MEFL]Engineering Sciences [physics]/Mechanics [physics.med-ph]/Fluids mechanics [physics.class-ph] ,regional pollen transport ,Pollen ,0103 physical sciences ,medicine ,wind ,Atmospheric turbulence ,Meso-NH ,[PHYS.MECA.MEFL]Physics [physics]/Mechanics [physics]/Fluid mechanics [physics.class-ph] ,010303 astronomy & astrophysics ,0105 earth and related environmental sciences ,genetically modified crop ,[PHYS.MECA.MEFL]Physics [physics]/Mechanics [physics]/Mechanics of the fluids [physics.class-ph] ,simulation model ,Plume ,Geography ,Deposition (aerosol physics) ,Agronomy ,pollen ,Biological dispersal ,cross-pollination - Abstract
chapitre 6; International audience; Recent evidence has shown that maize pollen can travel and remain viable at regional scales, which opens the possibility for long-distance cross-pollination. Here, we first report results obtained on small plots of white-kernel maize used as pollen traps, in a region with extensive maize cultivation, demonstrating that cross-pollination can indeed occur at several kilometres from the nearest source field. We also used the atmospheric Meso-NH model to better understand long-range dispersal of maize pollen. Simulations were performed over Southwest France during the maize pollination period. When compared with airborne measurements, the model provides good estimates of pollen concentration throughout the atmospheric boundary layer. It allows the pollen plume to be characterized during the day and permits the production of deposition maps of accumulated viable pollen. These results quantify long-distance pollen deposition; they show that background levels of cross-pollination are unavoidable at the regional scale and support the use of low purity thresholds by supply chain operators. more...
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- 2012
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43. Downwind evolution of scalar fluxes and surface resistance under conditions of local advection. Part I: a reappraisal of boundary conditions
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B. Itier, Jean-Pierre Lagouarde, K.J. McAneney, and Yves Brunet
- Subjects
Atmospheric Science ,Global and Planetary Change ,Leading edge ,Meteorology ,Advection ,Scalar (mathematics) ,Forestry ,Limiting ,Mechanics ,Flux (metallurgy) ,Exponent ,Environmental science ,Boundary value problem ,Agronomy and Crop Science ,Sheet resistance - Abstract
Various models have been proposed to predict changes in scalar concentrations and surface fluxes following an abrupt change in surface conditions. In most cases the boundary conditions used to describe the surface represent limiting cases such as a step change in either concentration, flux or surface resistance. Three main conclusions emerge from a review of experimental results published thus far. Firstly, a dry-to-wet transition can be treated as a step change in concentration, after which the difference between the downwind and upwind surface fluxes show a power-law dependence on distance from the leading edge with an exponent of the order of − 1 6 . Secondly, wet-to-dry transitions should be treated as resulting in a step change in flux. This has not always been appreciated. Thirdly, a dry-to-moist (e.g. irrigated) transition is shown to resemble more closely a step change in flux than a step change in surface resistance. This can only be explained if stomatal resistance varies in conjunction with downwind changes in saturation deficit. We propose a simple analytical model to describe the streamwise change in surface resistance in the limit of a step change in flux. A scarcity of published data suitable for validation of this model has led us to undertake a new experimental investigation. This experiment is the subject of a companion paper. more...
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- 1994
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44. Downwind evolution of scalar fluxes and surface resistance under conditions of local advection. Part II: measurements over barley
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J. McAneney, Yves Brunet, B. Itier, and Jean-Pierre Lagouarde
- Subjects
Atmospheric Science ,Global and Planetary Change ,Meteorology ,Advection ,Eddy covariance ,Humidity ,Forestry ,Sensible heat ,Atmospheric sciences ,Flux (metallurgy) ,Evapotranspiration ,Latent heat ,Environmental science ,Hordeum vulgare ,Agronomy and Crop Science - Abstract
It has been suggested in Part I of this paper that, after a dryland-to-irrigated transition, the surface sensible and latent heat fluxes may exhibit little change with downstream distance from the leading edge. It was argued that such step changes in surface fluxes could be caused by a feedback mechanism between surface resistance and changing saturation deficit. A simple model was derived for describing the streamwise change in surface resistance leading to such a step change in flux. The aim of the present paper is to test these assumptions against experimental data acquired specifically for this purpose. Measurements were performed over a transition between dryland and irrigated barley. Eddy covariance determinations of sensible heat flux at a height of 1 m showed little variation downwind of the transition and, once corrected from the footprint effect, exhibited patterns roughly compatible with a step change in surface flux. Transects of radiative temperature, and air temperature and humidity above the crop, also showed downwind changes in good agreement with the expected variation. The most convincing results were obtained from measurements of stomatal and canopy resistance, whose downwind variation was close to that required by a step change in evapotranspiration. more...
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- 1994
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45. Risk, Financing and the Optimal Number of Suppliers
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Jussi Keppo, Pierre-Yves Brunet, Volodymyr Babich, Goker Aydin, and Romesh Saigal
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Procurement ,Trade credit ,Internal financing ,Supplier relationship management ,Supply chain ,Developing country ,Business ,Fixed cost ,Risk financing ,Industrial organization - Abstract
Should firms in developed economies work with more or fewer suppliers than firms in developing economies? More generally, how does the number of suppliers for a firm depend on the firm’s economic environment? To answer these questions we identify several economic and business factors that might affect the number of suppliers (and that separate developed and developing economies): supply risk, fixed costs of working with suppliers, and access to financing (particularly trade-credit financing). more...
- Published
- 2011
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46. Long-distance edge effects in a pine forest with a deep and sparse trunk space: in situ and numerical experiments
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Jean-Marc Bonnefond, Eric Lamaud, M. Irvine, Yves Brunet, Sylvain Dupont, Écologie fonctionnelle et physique de l'environnement (EPHYSE), Institut National de la Recherche Agronomique (INRA), GENCI-IDRIS [2009-i2009011833], and Ephyse cluster more...
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Canopy ,Atmospheric Science ,010504 meteorology & atmospheric sciences ,[SDV]Life Sciences [q-bio] ,Mesoscale meteorology ,Flux ,Edge (geometry) ,Atmospheric sciences ,01 natural sciences ,010305 fluids & plasmas ,TRUNK SPACE ,SECONDARY WIND MAXIMUM ,0103 physical sciences ,Astrophysics::Solar and Stellar Astrophysics ,Pressure gradient ,ComputingMilieux_MISCELLANEOUS ,0105 earth and related environmental sciences ,Hydrology ,Global and Planetary Change ,Jet (fluid) ,Tree canopy ,LARGE-EDDY SIMULATION ,Turbulence ,PIN MARITIME ,Forestry ,15. Life on land ,[SDE]Environmental Sciences ,MOMENTUM FLUX BUDGET ,EDGE FLOW ,FOREST CANOPY ,Agronomy and Crop Science ,Geology - Abstract
As forest edges are a major source of heterogeneity in fragmented landscapes, the atmospheric flow over forested areas is often under their influence. Understanding how far the upstream edge has an impact on the turbulent wind flow in a forest canopy is important, in particular for scalar flux measurement. In this study, edge and stand flows over a maritime pine forest characterized by a dense crown layer located above a deep and sparse trunk space are analysed in detail from in situ measurements and large-eddy simulations (LES). The LES model used here appears to simulate remarkably well most characteristics of the turbulent wind flow for this particular canopy structure. It is shown that the main characteristics of the edge flow in this case differ from those usually observed in forests with a more uniform vertical foliage distribution. The main differences are (i) the development of turbulence above the canopy occurring closer to the edge, (ii) the absence of a well-defined enhanced gust zone around the top of the canopy, (iii) the presence of a large secondary wind maximum within the trunk space, and (iv) the development of a positive momentum flux layer below the crown layer. Most of these differences are related to the presence of a substantial sub-canopy wind jet induced by the wind flow through the trunk space at the edge. The secondary velocity maximum induced by this wind jet differs from that observed in homogeneous stand conditions, where it seems to be related to the mesoscale pressure gradient. The wind jet appears to decrease very slowly with distance from the edge, so that edge effects are still significant at 9 h from the edge (where h is the mean canopy height). The length of the adjustment region is shown to be greater than 10–15 h , and to depend on the depth of the trunk space. In very fragmented forested areas with deep and sparse trunk space, within-canopy flow may always be under the influence of edges. more...
- Published
- 2011
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47. The FluxSAP 2010 hydroclimatological experimental campaign over an heterogeneous urban area
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Patrice Mestayer, Bagga, I., Isabelle Calmet, Fontanilles, G., Dominique Gaudin, Lee, J. H., Thibaud Piquet, Jean-Michel Rosant, Katia Chancibault, Laurent Lebouc, Laetitia Letellier, Marie-Laure Mosini, Fabrice Rodriguez, Jean-Marc Rouaud, Maeva Sabre, Yves Tétard, Aurore Brut, Jean-Louis Selves, Pierre-Adrien Solignac, Yves Brunet, Sylvia Dayau, Mark Rankin Irvine, Jean-Pierre Lagouarde, Zeineb Kassouk, Patrick Launeau, Olivier Connan, Pauline Defenouillère, Mathieu Goriaux, Didier Hebert, Letellier, B., Mario, D., Georges Najjar, Françoise Nerry, Céline Quentin, Romain Biron, Jean-Martial Cohard, Galvez, J., Klein, P., Centre National de la Recherche Scientifique (CNRS), École Centrale de Nantes (ECN), Laboratoire de mécanique des fluides (LMF), École Centrale de Nantes (ECN)-Centre National de la Recherche Scientifique (CNRS), Institut Français des Sciences et Technologies des Transports, de l'Aménagement et des Réseaux (IFSTTAR), Centre Scientifique et Technique du Bâtiment (CSTB), Centre d'études spatiales de la biosphère (CESBIO), 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 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 de Recherche pour l’Agriculture, l’Alimentation et l’Environnement (INRAE), Écologie fonctionnelle et physique de l'environnement (EPHYSE), Institut National de la Recherche Agronomique (INRA), Laboratoire de Planétologie et Géodynamique [UMR 6112] (LPG), Université d'Angers (UA)-Université de Nantes - UFR des Sciences et des Techniques (UN UFR ST), Université de Nantes (UN)-Université de Nantes (UN)-Institut national des sciences de l'Univers (INSU - CNRS)-Centre National de la Recherche Scientifique (CNRS), Institut de Radioprotection et de Sûreté Nucléaire (IRSN), Laboratoire des Sciences de l'Image, de l'Informatique et de la Télédétection (LSIIT), Laboratoire d'étude des transferts en hydrologie et environnement (LTHE), 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)-Institut National Polytechnique de Grenoble (INPG)-Centre National de la Recherche Scientifique (CNRS), School of Meteorology, University of Oklahoma (OU), Centre National de la Recherche Scientifique (CNRS)-Institut de Recherche pour le Développement (IRD)-Institut National de Recherche pour l’Agriculture, l’Alimentation et l’Environnement (INRAE)-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 National Polytechnique de Grenoble (INPG)-Centre National de la Recherche Scientifique (CNRS)-Observatoire des Sciences de l'Univers de Grenoble (OSUG), and 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)-Institut national des sciences de l'Univers (INSU - CNRS)-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)-Institut national des sciences de l'Univers (INSU - CNRS)-Université Savoie Mont Blanc (USMB [Université de Savoie] [Université de Chambéry]) more...
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climat ,[SDE.MCG]Environmental Sciences/Global Changes ,HYDROLOGIE ,URBAN STUDIES ,CLIMATOLOGY ,HYDROLOGY ,VEGDUD PROGRAM ,environnement ,zone urbaine ,[PHYS.MECA.MEFL]Physics [physics]/Mechanics [physics]/Fluid mechanics [physics.class-ph] ,Milieux et Changements globaux ,végétation ,ComputingMilieux_MISCELLANEOUS - Abstract
International audience
- Published
- 2011
48. Modelling waving crops using large-eddy simulation: Comparison with experiments and a linear stability analysis
- Author
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Sylvain Dupont, E. de Langre, Frédérick P. Gosselin, Pascal Hémon, Charlotte Py, Yves Brunet, Écologie fonctionnelle et physique de l'environnement (EPHYSE), Institut National de la Recherche Agronomique (INRA), Laboratoire d'hydrodynamique (LadHyX), École polytechnique (X)-Centre National de la Recherche Scientifique (CNRS), Matière et Systèmes Complexes (MSC (UMR_7057)), Université Paris Diderot - Paris 7 (UPD7)-Centre National de la Recherche Scientifique (CNRS), Écologie fonctionnelle et physique de l'environnement (EPHYSE - UR1263), and Centre National de la Recherche Scientifique (CNRS)-École polytechnique (X) more...
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010504 meteorology & atmospheric sciences ,Field (physics) ,WIND VELOCITY ,Airflow ,Poromechanics ,01 natural sciences ,Wind speed ,010305 fluids & plasmas ,[SPI.MECA.MEFL]Engineering Sciences [physics]/Mechanics [physics.med-ph]/Fluids mechanics [physics.class-ph] ,CANOPY ,0103 physical sciences ,[PHYS.MECA.MEFL]Physics [physics]/Mechanics [physics]/Fluid mechanics [physics.class-ph] ,0105 earth and related environmental sciences ,LARGE-EDDY SIMULATION ,[PHYS.MECA.MEFL]Physics [physics]/Mechanics [physics]/Mechanics of the fluids [physics.class-ph] ,Mechanical Engineering ,Mode (statistics) ,Mechanics ,15. Life on land ,Condensed Matter Physics ,LES MODEL ,Vibration ,Mechanics of Materials ,Drag ,Geology ,Large eddy simulation - Abstract
International audience; In order to investigate the possibility of modelling plant motion at the landscape scale, an equation for crop plant motion, forced by an instantaneous velocity field, is introduced in a large-eddy simulation (LES) airflow model, previously validated over homogeneous and heterogeneous canopies. The canopy is simply represented as a poroelastic continuous medium, which is similar in its discrete form to an infinite row of identical oscillating stems. Only one linear mode of plant vibration is considered. Two-way coupling between plant motion and the wind flow is insured through the drag force term. The coupled model is validated on the basis of a comparison with measured movements of an alfalfa crop canopy. It is also compared with the outputs of a linear stability analysis. The model is shown to reproduce the well-known phenomenon of honami which is typical of wave-like crop motions on windy days. The wavelength of the main coherent waving patches, extracted using a bi-orthogonal decomposition (BOD) of the crop velocity fields, is in agreement with that deduced from video recordings. The main spatial and temporal characteristics of these waving patches exhibit the same variation with mean wind velocity as that observed with the measurements. However they differ from the coherent eddy structures of the wind flow at canopy top, so that coherent waving patches cannot be seen as direct signatures of coherent eddy structures. Finally, it is shown that the impact of crop motion on the wind dynamics is negligible for current wind speed values. No lock-in mechanism of coherent eddy structures on plant motion is observed, in contradiction with the linear stability analysis. This discrepancy may be attributed to the presence of a nonlinear saturation mechanism in LES. © 2010 Cambridge University Press. more...
- Published
- 2010
- Full Text
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49. Flux-gradient relationships above tall plant canopies
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Yves Brunet, Pierre Cellier, Unité de recherches en bioclimatologie, Institut National de la Recherche Agronomique (INRA), and Unité de bioclimatologie
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Atmospheric Science ,Global and Planetary Change ,010504 meteorology & atmospheric sciences ,Meteorology ,[SDE.MCG]Environmental Sciences/Global Changes ,Flow (psychology) ,0207 environmental engineering ,Scalar (physics) ,Forestry ,02 engineering and technology ,Aerodynamics ,Mechanics ,Energy budget ,01 natural sciences ,Wind speed ,Momentum ,Environmental science ,Surface layer ,RAPPORT DE BOWEN ,020701 environmental engineering ,Agronomy and Crop Science ,Water vapor ,0105 earth and related environmental sciences - Abstract
International audience; The classical flux-gradient relationships derived from the surface layer similarity theory have been known for a long time not to be valid just above plant canopies; within the framework of first-order closure, all the published studies have indeed shown that in the so-called 'roughness sublayer' the momentum and/or scalar diffusivities are enhanced above their inertial layer values. Alternate relationships that would be adequate in this region of the flow are, therefore, required for estimating heat and water vapour fluxes by the aerodynamic method or for calculating the aerodynamic resistances above tall canopies. A simple enhancement model may be a suitable basis for such relationships, provided it can be validated against existing or new experimental data. For this purpose, measurements of wind speed, air temperature and humidity profiles were made above a maize crop, along with other standard energy budget measurements. They confirm the existence of a roughness sublayer just above the canopy, in which the profiles depart significantly from the inertial layer similarity forms. This sublayer was found to extend up to about twice the canopy height. The measurements, performed throughout the entire sublayer and above it, give a precise picture of the evolution of the discrepancies with height, which can be interpreted in terms of enhanced diffusivities. Our results allow us to derive simple generalized flux-profile relationships that can be used to calculate the fluxes of heat and water vapour (and any other scalar) from two or more measurement levels, in the same way as with the classical aerodynamic method. These new relationships are shown to be compatible with most of the results already published, obtained over a wide range of canopies. The errors made when using the inertial layer relationships are quantified for typical experimental situations. more...
- Published
- 1992
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50. Effect of land use on carbon dioxide, water vapour and energy exchange over terrestrial ecosystems in Southwestern France during the CERES campaign
- Author
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Eric Ceschia, Pierre Béziat, Jan Elbers, N. Jarosz, O. Traullé, Yves Brunet, Ronald Hutjes, Jean-Marc Bonnefond, Jean-Christophe Calvet, Centre d'études spatiales de la biosphère (CESBIO), 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 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 de Recherche pour l’Agriculture, l’Alimentation et l’Environnement (INRAE), Écologie fonctionnelle et physique de l'environnement (EPHYSE), Institut National de la Recherche Agronomique (INRA), Météo-France Direction Interrégionale Sud-Est (DIRSE), Météo-France, Wageningen University and Research Centre (WUR), Centre National de la Recherche Scientifique (CNRS)-Institut de Recherche pour le Développement (IRD)-Institut National de Recherche pour l’Agriculture, l’Alimentation et l’Environnement (INRAE)-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), and Météo France more...
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0106 biological sciences ,Canopy ,Irrigation ,010504 meteorology & atmospheric sciences ,[SDV]Life Sciences [q-bio] ,01 natural sciences ,Grassland ,Forest ecology ,Alterra - Centre for Water and Climate ,Life Science ,Ecosystem ,Wageningen Environmental Research ,Bowen ratio ,ComputingMilieux_MISCELLANEOUS ,0105 earth and related environmental sciences ,2. Zero hunger ,Forest floor ,geography ,geography.geographical_feature_category ,WIMEK ,PIN MARITIME ,15. Life on land ,Agronomy ,[SDE]Environmental Sciences ,Environmental science ,Terrestrial ecosystem ,MESURES DE FLUX ,010606 plant biology & botany ,Alterra - Centrum Water en Klimaat - Abstract
Eddy fluxes were measured over different ecosystems, winter and summer crops, a maritime pine forest at different stages of development and grassland, from 17 May to 26 June 2005 in the southwestern region of France. During the experiment, summer crops started growing whereas winter crops and grassland achieved their senescence. Comparatively, the other ecosystems had a much slower growth emphasized by soil water deficit at forest sites. The ten ecosystems showed different partitioning of available energy. Net radiation was the highest above the maritime pine forest, followed, in decreasing order, by the crops, the vineyard and the grassland. Over the whole campaign period, the Bowen ratio (β=H/LE) was larger above the forest sites than for the other sites. The various vegetation types also showed contrasting net ecosystem exchange (NEE) dynamics following their growth status and respective behaviour in response to drought. Both the clearcut and summer crops before irrigation and plant growth behaved as sources of CO2, whereas the vineyard, the mature forest and winter crops acted as sinks. However the maize crops became substantial sinks of CO2 after the start of irrigation and canopy growth, with fluxes twice as large as for the mature pine forest. Finally, throughout the experiment, forest, grassland and crops sequestrated from about 50 gC m−2 to 230 gC m−2, while the cleacut and the beans crop rejected about 30 gC m−2. These results support the idea that converting a mature forest to a clearcut or bare soil available to agricultural use enhances the sensible heat flux and shifts the ecosystem from a sink to a source of carbon. more...
- Published
- 2009
- Full Text
- View/download PDF
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