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1. Wave-Scattering processes: path-integrals designed for the numerical handling of complex geometries

Author

Dauchet, Jérémi, Charon, Julien, Brunel, Laurent, Coustet, Christophe, Blanco, Stéphane, Cornet, Jean-François, Hafi, Mouna El, Eymet, Vincent, Forest, Vincent, Fournier, Richard, Gros, Fabrice, Piaud, Benjamin, and Vourc'h, Thomas

Subjects
Physics - Biological Physics, Physics - Computational Physics, Physics - Data Analysis, Statistics and Probability, Physics - Optics
Abstract

Relying on Feynman-Kac path-integral methodology, we present a new statistical perspective on wave single-scattering by complex three-dimensional objects. The approach is implemented on three models -- Schiff approximation, Born approximation and rigorous Born series -- and usual interpretative difficulties such as the analysis of moments over scatterer distributions (size, orientation, shape...) are addressed. In terms of computational contribution, we show that commonly recognized features of Monte Carlo method with respect to geometric complexity can now be available when solving electromagnetic scattering.

Published
2022

2. The 'teapot in a city': a paradigm shift in urban climate modeling

Author

Villefranque, Najda, Hourdin, Frédéric, d'Alençon, Louis, Blanco, Stéphane, Boucher, Olivier, Caliot, Cyril, Coustet, Christophe, Dauchet, Jérémi, Hafi, Mouna El, Farges, Olivier, Forest, Vincent, Fournier, Richard, Masson, Valéry, Piaud, Benjamin, and Schoetter, Robert

Subjects
Physics - Physics and Society, Physics - Atmospheric and Oceanic Physics, Physics - Computational Physics, Physics - Data Analysis, Statistics and Probability
Abstract

Urban areas are a high-stake target of climate change mitigation and adaptation measures. To understand, predict and improve the energy performance of cities, the scientific community develops numerical models that describe how they interact with the atmosphere through heat and moisture exchanges at all scales. In this review, we present recent advances that are at the origin of last decade's revolution in computer graphics, and recent breakthroughs in statistical physics that extend well established path-integral formulations to non-linear coupled models. We argue that this rare conjunction of scientific advances in mathematics, physics, computer and engineering sciences opens promising avenues for urban climate modeling and illustrate this with coupled heat transfer simulations in complex urban geometries under complex atmospheric conditions. We highlight the potential of these approaches beyond urban climate modeling, for the necessary appropriation of the issues at the heart of the energy transition by societies., Comment: Accepted for publication in Science Advances

Published
2022

6. Path-tracing Monte Carlo Library for 3D Radiative Transfer in Highly Resolved Cloudy Atmospheres

Author

Villefranque, Najda, Couvreux, Fleur, Fournier, Richard, Blanco, Stéphane, Cornet, Céline, Eymet, Vincent, Forest, Vincent, and Tregan, Jean-Marc

Subjects
Physics - Computational Physics
Abstract

Interactions between clouds and radiation are at the root of many difficulties in numerically predicting future weather and climate and in retrieving the state of the atmosphere from remote sensing observations. The large range of issues related to these interactions, and in particular to three-dimensional interactions, motivated the development of accurate radiative tools able to compute all types of radiative metrics, from monochromatic, local and directional observables, to integrated energetic quantities. In the continuity of this community effort, we propose here an open-source library for general use in Monte Carlo algorithms. This library is devoted to the acceleration of path-tracing in complex data, typically high-resolution large-domain grounds and clouds. The main algorithmic advances embedded in the library are those related to the construction and traversal of hierarchical grids accelerating the tracing of paths through heterogeneous fields in null-collision (maximum cross-section) algorithms. We show that with these hierarchical grids, the computing time is only weakly sensitivive to the refinement of the volumetric data. The library is tested with a rendering algorithm that produces synthetic images of cloud radiances. Two other examples are given as illustrations, that are respectively used to analyse the transmission of solar radiation under a cloud together with its sensitivity to an optical parameter, and to assess a parametrization of 3D radiative effects of clouds., Comment: Submitted to JAMES, revised and submitted again (this is v2)

Published
2019
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7. Complementary Finite Element and Monte-Carlo Methods to Solve Industrial Thermal Problems

Author

Peniguel Christophe, Rupp Isabelle, Fournier Richard, Blanco Stéphane, Eymet Vincent, Forest Vincent, and Coustet Christophe

Subjects
Physics, QC1-999
Abstract

This paper presents the integration of a Monte-Carlo solver inside SYRTHES, an open-source thermal code, originally based on finite elements method. Insensitive to both the geometric complexity of the model and the fineness of its discretization, this stochastic method is a good complementary option to simulate large configurations with specific locations of interest. Radiation, conduction and convection can be combined to solve thermal problems in complex geometries. The Monte-Carlo method is described before showing its integration in the code SYRTHES. Comparisons against results obtained thanks to finite elements and Monte-Carlo approaches or analytical solutions are presented. Finally, industrial cases illustrate the advantages of using these two complementary approaches.

Published
2024
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8. Addressing nonlinearities in Monte Carlo

Author

Dauchet, Jérémi, Bezian, Jean-Jacques, Blanco, Stéphane, Caliot, Cyril, Charon, Julien, Coustet, Christophe, Hafi, Mouna El, Eymet, Vincent, Farges, Olivier, Forest, Vincent, Fournier, Richard, Galtier, Mathieu, Gautrais, Jacques, Khuong, Anaïs, Pelissier, Lionel, Piaud, Benjamin, Roger, Maxime, Terrée, Guillaume, and Weitz, Sebastian

Subjects
Physics - Computational Physics
Abstract

Monte Carlo is famous for accepting model extensions and model refinements up to infinite dimension. However, this powerful incremental design is based on a premise which has severely limited its application so far: a state-variable can only be recursively defined as a function of underlying state-variables if this function is linear. Here we show that this premise can be alleviated by projecting nonlinearities onto a polynomial basis and increasing the configuration space dimension. Considering phytoplankton growth in light-limited environments, radiative transfer in planetary atmospheres, electromagnetic scattering by particles, and concentrated solar power plant production, we prove the real-world usability of this advance in four test cases which were previously regarded as impracticable using Monte Carlo approaches. We also illustrate an outstanding feature of our method when applied to acute problems with interacting particles: handling rare events is now straightforward. Overall, our extension preserves the features that made the method popular: addressing nonlinearities does not compromise on model refinement or system complexity, and convergence rates remain independent of dimension. Published: Dauchet J, Bezian J-J, Blanco S, Caliot C, Charon J, Coustet C, El Hafi M, Eymet V, Farges O, Forest V, Fournier R, Galtier M, Gautrais J, Khuong A, Pelissier L, Piaud B, Roger M, Terr\'ee G, Weitz S (2018) Addressing nonlinearities in Monte Carlo. Sci. Rep. 8: 13302, DOI:10.1038/s41598-018-31574-4, Comment: 36 pages, 6 figues

Published
2016
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9. Spectrally refined unbiased Monte Carlo estimate of the Earth’s global radiative cooling

Author

Nyffenegger-Péré, Yaniss, primary, Armante, Raymond, additional, Bati, Mégane, additional, Blanco, Stéphane, additional, Dufresne, Jean-Louis, additional, Hafi, Mouna El, additional, Eymet, Vincent, additional, Forest, Vincent, additional, Fournier, Richard, additional, Gautrais, Jacques, additional, Lebrun, Raphaël, additional, Mellado, Nicolas, additional, Mourtaday, Nada, additional, and Paulin, Mathias, additional

Published
2024
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10. Wave-Scattering processes: path-integrals designed for thenumerical handling of complex geometries

Author

DAUCHET, Jeremi, primary, Charon, Julien, additional, Brunel, Laurent, additional, coustet, Christophe, additional, blanco, stéphane, additional, Cornet, Jean-françois, additional, el hafi, mouna, additional, eymet, vincent, additional, forest, Vincent, additional, fournier, richard, additional, gros, fabrice, additional, piaud, benjamin, additional, terrée, guillaume, additional, and vourc h, thomas, additional

Published
2023
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12. Coupling radiative, conductive and convective heat-transfers in a single Monte Carlo algorithm: A general theoretical framework for linear situations

Author

Tregan, Jean Marc, primary, Amestoy, Jean Luc, additional, Bati, Megane, additional, Bezian, Jean-Jacques, additional, Blanco, Stéphane, additional, Brunel, Laurent, additional, Caliot, Cyril, additional, Charon, Julien, additional, Cornet, Jean-Francois, additional, Coustet, Christophe, additional, d’Alençon, Louis, additional, Dauchet, Jeremi, additional, Dutour, Sebastien, additional, Eibner, Simon, additional, El Hafi, Mouna, additional, Eymet, Vincent, additional, Farges, Olivier, additional, Forest, Vincent, additional, Fournier, Richard, additional, Galtier, Mathieu, additional, Gattepaille, Victor, additional, Gautrais, Jacques, additional, He, Zili, additional, Hourdin, Frédéric, additional, Ibarrart, Loris, additional, Joly, Jean-Louis, additional, Lapeyre, Paule, additional, Lavieille, Pascal, additional, Lecureux, Marie-Helene, additional, Lluc, Jacques, additional, Miscevic, Marc, additional, Mourtaday, Nada, additional, Nyffenegger-Péré, Yaniss, additional, Pelissier, Lionel, additional, Penazzi, Lea, additional, Piaud, Benjamin, additional, Rodrigues-Viguier, Clément, additional, Roques, Gisele, additional, Roger, Maxime, additional, Saez, Thomas, additional, Terrée, Guillaume, additional, Villefranque, Najda, additional, Vourc’h, Thomas, additional, and Yaacoub, Daniel, additional

Published
2023
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13. Résolution d'un problème de transferts thermiques couplés en géométrie urbaine par la méthode Monte Carlo

Author

Retailleau, Florent, Schoetter, Robert, Forest, Vincent, Caliot, Cyril, Laboratoire de Mathématiques et de leurs Applications [Pau] (LMAP), Université de Pau et des Pays de l'Adour (UPPA)-Centre National de la Recherche Scientifique (CNRS), Centre national de recherches météorologiques (CNRM), Institut national des sciences de l'Univers (INSU - CNRS)-Observatoire Midi-Pyrénées (OMP), Institut de Recherche pour le Développement (IRD)-Université Toulouse III - Paul Sabatier (UT3), Université de Toulouse (UT)-Université de Toulouse (UT)-Institut national des sciences de l'Univers (INSU - CNRS)-Centre National d'Études Spatiales [Toulouse] (CNES)-Centre National de la Recherche Scientifique (CNRS)-Météo-France -Institut de Recherche pour le Développement (IRD)-Université Toulouse III - Paul Sabatier (UT3), Université de Toulouse (UT)-Université de Toulouse (UT)-Institut national des sciences de l'Univers (INSU - CNRS)-Centre National d'Études Spatiales [Toulouse] (CNES)-Centre National de la Recherche Scientifique (CNRS)-Météo-France -Centre National de la Recherche Scientifique (CNRS), and ANR-21-CE46-0013,MC2,Simulations Monte-Carlo pour la Météorologie et la Climatologie(2021)

Subjects
[SPI]Engineering Sciences [physics]
Abstract

International audience; Pour prévenir et s’adapter aux canicules en zone urbaine, il est nécessaire de disposer d’outilsnumériques de prédiction des transferts thermiques couplés qui prennent en compte la complexitégéométrique de la ville. L’étude qui suit présente un modèle probabiliste de transferts couplés conducto-radiatif linéarisé et transitoire. La méthode de Monte-Carlo (MC) est utilisée pour la résolution dumodèle probabiliste avec une randomisation des contributions des différents modes de transferts dechaleur à la paroi. Nous faisons ici la preuve de concept du passage à l’échelle à l’aide du programmeStardis.

Published
2023

14. ESTIMATING ATMOSPHERIC RADIATIVE FORCINGS USING SENSITIVITY MONTE CARLO METHODS

Author

Mourtaday, Nada Chems, primary, Bati, Megane, additional, Blanco, Stephane, additional, Dufresne, Jean-Louis, additional, El Hafi, Mouna, additional, Eymet, Vincent, additional, Forest, Vincent, additional, Fournier, Richard, additional, Gautrais, Jacques, additional, Lapeyre, Paule, additional, Mellado, Nicolas, additional, Nyffenegger-Pere, Yaniss, additional, Paulin, Mathias, additional, and Villefranque, Najda, additional

Published
2023
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15. Advection, diffusion and linear transport in a single path-sampling Monte-Carlo algorithm : getting insensitive to geometrical refinement

Author

Ibarrart, Loris, Blanco, Stéphane, Caliot, Cyril, Dauchet, Jérémi, Eibner, Simon, El-Hafi, Mouna, Farges, Olivier, Forest, Vincent, Fournier, Richard, Gautrais, Jacques, Konduru, Raj, Penazzi, Léa, Tregan, Jean-Marc, Vourc’h, Thomas, Centre de recherche d'Albi en génie des procédés des solides divisés, de l'énergie et de l'environnement (RAPSODEE), Centre National de la Recherche Scientifique (CNRS)-IMT École nationale supérieure des Mines d'Albi-Carmaux (IMT Mines Albi), Institut Mines-Télécom [Paris] (IMT)-Institut Mines-Télécom [Paris] (IMT), LAboratoire PLasma et Conversion d'Energie (LAPLACE), Université Toulouse III - Paul Sabatier (UT3), Université Fédérale Toulouse Midi-Pyrénées-Université Fédérale Toulouse Midi-Pyrénées-Centre National de la Recherche Scientifique (CNRS)-Institut National Polytechnique (Toulouse) (Toulouse INP), Université Fédérale Toulouse Midi-Pyrénées, Procédés, Matériaux et Energie Solaire (PROMES), Université de Perpignan Via Domitia (UPVD)-Centre National de la Recherche Scientifique (CNRS), Institut Pascal (IP), Centre National de la Recherche Scientifique (CNRS)-Université Clermont Auvergne (UCA)-Institut national polytechnique Clermont Auvergne (INP Clermont Auvergne), Université Clermont Auvergne (UCA)-Université Clermont Auvergne (UCA), Laboratoire Énergies et Mécanique Théorique et Appliquée (LEMTA ), Université de Lorraine (UL)-Centre National de la Recherche Scientifique (CNRS), Meso-Star, Groupe de Recherche Energétique, Plasmas et Hors Equilibre (LAPLACE-GREPHE), Université Fédérale Toulouse Midi-Pyrénées-Université Toulouse III - Paul Sabatier (UT3), Centre de Recherches sur la Cognition Animale (CRCA), Institut des sciences du cerveau de Toulouse. (ISCT), Université Toulouse - Jean Jaurès (UT2J)-Université Toulouse III - Paul Sabatier (UT3), Université Fédérale Toulouse Midi-Pyrénées-Université Fédérale Toulouse Midi-Pyrénées-CHU Toulouse [Toulouse]-Institut National de la Santé et de la Recherche Médicale (INSERM)-Centre National de la Recherche Scientifique (CNRS)-Université Toulouse - Jean Jaurès (UT2J)-Université Toulouse III - Paul Sabatier (UT3), Université Fédérale Toulouse Midi-Pyrénées-Université Fédérale Toulouse Midi-Pyrénées-CHU Toulouse [Toulouse]-Institut National de la Santé et de la Recherche Médicale (INSERM)-Centre National de la Recherche Scientifique (CNRS)-Centre National de la Recherche Scientifique (CNRS)-Centre de Biologie Intégrative (CBI), Université Fédérale Toulouse Midi-Pyrénées-Université Fédérale Toulouse Midi-Pyrénées-Centre National de la Recherche Scientifique (CNRS)-Centre National de la Recherche Scientifique (CNRS), ANR-16-CE01-0010,HIGH-TUNE,Amélioration et calibration des paramétrisations des nuages de couche limite à partir de simulations haute résolution(2016), ANR-21-CE46-0013,MC2,Simulations Monte-Carlo pour la Météorologie et la Climatologie(2021), ANR-18-CE46-0012,MCG-Rad,Calcul par Monte-Carlo des forçages radiatifs à l'échelle globale(2018), ANR-16-IDEX-0001,CAP 20-25,CAP 20-25(2016), ANR-10-LABX-0016,IMoBS3,Innovative Mobility : Smart and Sustainable Solutions(2010), and ANR-10-LABX-0022,SOLSTICE,Solar Energy, Science, Technology and Innovation for Energy Conversion(2010)

Subjects
[PHYS.PHYS.PHYS-COMP-PH]Physics [physics]/Physics [physics]/Computational Physics [physics.comp-ph], [PHYS.PHYS.PHYS-BIO-PH]Physics [physics]/Physics [physics]/Biological Physics [physics.bio-ph], [SPI.MECA.THER]Engineering Sciences [physics]/Mechanics [physics.med-ph]/Thermics [physics.class-ph], [SPI.OPTI]Engineering Sciences [physics]/Optics / Photonic, [SPI.GPROC]Engineering Sciences [physics]/Chemical and Process Engineering, [PHYS.PHYS.PHYS-DATA-AN]Physics [physics]/Physics [physics]/Data Analysis, Statistics and Probability [physics.data-an]
Abstract

We address the question of numerically simulating the coupling of diffusion, advection and one-speed linear transport with the specific objective of handling increases of the amount, the geometrical refinement and the accuracy level of input data. The computer graphics research community has succeeded in designing Monte Carlo algorithms simulating linear radiation transport in physically realistic scenes with numerical costs that are insensitive to geometrical refinement: adding more details to the scene description does not affect the computation time. The corresponding benefits in terms of engineering flexibility are already fully integrated in the cinema industry and are gradually inherited by the video game industry. We show here that the same insensitivity to the complexity of the geometrical description can also be achieved when considering one-speed linear transport not only alone but coupled with diffusion and advection. Pure linear-transport paths are replaced with advection-diffusion/linear-transport paths constituted of subpaths, each representing one of the three physical phenomena in a recursive manner. Illustration is made with a porous medium involving up to 10000 pores, the computation time being strictly independent of the number of pores.

Published
2022

17. Addressing nonlinearities in Monte Carlo

Author

Dauchet, Jérémi, Bezian, Jean-Jacques, Blanco, Stéphane, Caliot, Cyril, Charon, Julien, Coustet, Christophe, El Hafi, Mouna, Eymet, Vincent, Farges, Olivier, Forest, Vincent, Fournier, Richard, Galtier, Mathieu, Gautrais, Jacques, Khuong, Anaïs, Pelissier, Lionel, Piaud, Benjamin, Roger, Maxime, Terrée, Guillaume, and Weitz, Sebastian

Published
2018
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18. Sampling molecular state transitions in a line-by-line Monte Carlo approach to estimate radiative forcing for climate change studies

Author

NYFFENEGGER-PERE, Yaniss, Blanco, Stéphane, Dufresne, Jean-Louis, El-Hafi, Mouna, Eymet, Vincent, Forest, Vincent, Fournier, Richard, Mellado, Nicolas, Mourtaday, Nada Chems, Paulin, Mathias, Groupe de Recherche Energétique, Plasmas et Hors Equilibre (LAPLACE-GREPHE), LAboratoire PLasma et Conversion d'Energie (LAPLACE), Université Toulouse III - Paul Sabatier (UT3), Université de Toulouse (UT)-Université de Toulouse (UT)-Centre National de la Recherche Scientifique (CNRS)-Institut National Polytechnique (Toulouse) (Toulouse INP), Université de Toulouse (UT)-Université Toulouse III - Paul Sabatier (UT3), Université de Toulouse (UT), Laboratoire de Météorologie Dynamique (UMR 8539) (LMD), Institut national des sciences de l'Univers (INSU - CNRS)-École polytechnique (X)-École des Ponts ParisTech (ENPC)-Sorbonne Université (SU)-Centre National de la Recherche Scientifique (CNRS)-Département des Géosciences - ENS Paris, École normale supérieure - Paris (ENS-PSL), Université Paris sciences et lettres (PSL)-Université Paris sciences et lettres (PSL)-École normale supérieure - Paris (ENS-PSL), Université Paris sciences et lettres (PSL)-Université Paris sciences et lettres (PSL), Institut Pierre-Simon-Laplace (IPSL (FR_636)), Université Paris sciences et lettres (PSL)-Université Paris sciences et lettres (PSL)-Université de Versailles Saint-Quentin-en-Yvelines (UVSQ)-Commissariat à l'énergie atomique et aux énergies alternatives (CEA)-Institut national des sciences de l'Univers (INSU - CNRS)-École polytechnique (X)-Centre National d'Études Spatiales [Toulouse] (CNES)-Sorbonne Université (SU)-Centre National de la Recherche Scientifique (CNRS)-Université Paris Cité (UPCité), Centre de recherche d'Albi en génie des procédés des solides divisés, de l'énergie et de l'environnement (RAPSODEE), Centre National de la Recherche Scientifique (CNRS)-IMT École nationale supérieure des Mines d'Albi-Carmaux (IMT Mines Albi), Institut Mines-Télécom [Paris] (IMT)-Institut Mines-Télécom [Paris] (IMT), Méso-Star, Structural Models and Tools in Computer Graphics (IRIT-STORM), Institut de recherche en informatique de Toulouse (IRIT), Université Toulouse Capitole (UT Capitole), Université de Toulouse (UT)-Université de Toulouse (UT)-Université Toulouse - Jean Jaurès (UT2J), Université de Toulouse (UT)-Centre National de la Recherche Scientifique (CNRS)-Institut National Polytechnique (Toulouse) (Toulouse INP), Université de Toulouse (UT)-Toulouse Mind & Brain Institut (TMBI), Université Toulouse - Jean Jaurès (UT2J), Université de Toulouse (UT)-Université de Toulouse (UT)-Université Toulouse III - Paul Sabatier (UT3), Université de Toulouse (UT)-Université Toulouse Capitole (UT Capitole), Laboratory of Atmospheric Physics (LAP) of the Aristotle University of Thessaloniki (AUTH), International Radiation Commission (IRC) of the International Association of Meteorology and Atmospheric Sciences (IAMAS), and ANR-18-CE46-0012,MCG-Rad,Calcul par Monte-Carlo des forçages radiatifs à l'échelle globale(2018)

Subjects
[SDU.STU.CL]Sciences of the Universe [physics]/Earth Sciences/Climatology, [PHYS.MECA.THER]Physics [physics]/Mechanics [physics]/Thermics [physics.class-ph], [INFO.INFO-GR]Computer Science [cs]/Graphics [cs.GR]
Abstract

International audience; A major challenge of the beginning of the century is the nation’s actions over the terrestrial climate to counter the global warming. This warming is caused by the human activity and in particular by the emission of important amounts of greenhouse gases. Its close understanding and precise estimate are necessary to take appropriate actions and one of the driving concepts along this line is radiative forcing. This forcing is defined as the difference between two Top Of Atmosphere (TOA) radiative fluxes, both integrated spatially over all the Earth and temporally over a climatic period, the difference being due to a change of one single parameter. Here we focus on the forcing to carbon dioxide. So, our question is the estimation of the difference between two integrated TOA fluxes, before and after we change the CO2 concentration field.

Published
2022

19. The “teapot in a city”: A paradigm shift in urban climate modeling

Author

Villefranque, Najda, primary, Hourdin, Frédéric, additional, d’Alençon, Louis, additional, Blanco, Stéphane, additional, Boucher, Olivier, additional, Caliot, Cyril, additional, Coustet, Christophe, additional, Dauchet, Jérémi, additional, El Hafi, Mouna, additional, Eymet, Vincent, additional, Farges, Olivier, additional, Forest, Vincent, additional, Fournier, Richard, additional, Gautrais, Jacques, additional, Masson, Valéry, additional, Piaud, Benjamin, additional, and Schoetter, Robert, additional

Published
2022
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20. Une estimation exacte du forçage radiatif par la méthode de Monte-Carlo

Author

NYFFENEGGER-PERE, Yaniss, Blanco, Stéphane, Dufresne, Jean-Louis, El-Hafi, Mouna, Eymet, Vincent, Forest, Vincent, Fournier, Richard, Paulin, Mathias, Mellado, Nicolas, Groupe de Recherche Energétique, Plasmas et Hors Equilibre (LAPLACE-GREPHE), LAboratoire PLasma et Conversion d'Energie (LAPLACE), Université Toulouse III - Paul Sabatier (UT3), Université de Toulouse (UT)-Université de Toulouse (UT)-Centre National de la Recherche Scientifique (CNRS)-Institut National Polytechnique (Toulouse) (Toulouse INP), Université de Toulouse (UT)-Université Toulouse III - Paul Sabatier (UT3), Université de Toulouse (UT), Institut Pierre-Simon-Laplace (IPSL (FR_636)), École normale supérieure - Paris (ENS-PSL), Université Paris sciences et lettres (PSL)-Université Paris sciences et lettres (PSL)-Université de Versailles Saint-Quentin-en-Yvelines (UVSQ)-Commissariat à l'énergie atomique et aux énergies alternatives (CEA)-Institut national des sciences de l'Univers (INSU - CNRS)-École polytechnique (X)-Centre National d'Études Spatiales [Toulouse] (CNES)-Sorbonne Université (SU)-Centre National de la Recherche Scientifique (CNRS)-Université Paris Cité (UPCité), Laboratoire de Météorologie Dynamique (UMR 8539) (LMD), Institut national des sciences de l'Univers (INSU - CNRS)-École polytechnique (X)-École des Ponts ParisTech (ENPC)-Sorbonne Université (SU)-Centre National de la Recherche Scientifique (CNRS)-Département des Géosciences - ENS Paris, Université Paris sciences et lettres (PSL)-Université Paris sciences et lettres (PSL)-École normale supérieure - Paris (ENS-PSL), Université Paris sciences et lettres (PSL)-Université Paris sciences et lettres (PSL), Centre de recherche d'Albi en génie des procédés des solides divisés, de l'énergie et de l'environnement (RAPSODEE), Centre National de la Recherche Scientifique (CNRS)-IMT École nationale supérieure des Mines d'Albi-Carmaux (IMT Mines Albi), Institut Mines-Télécom [Paris] (IMT)-Institut Mines-Télécom [Paris] (IMT), Méso-Star, Structural Models and Tools in Computer Graphics (IRIT-STORM), Institut de recherche en informatique de Toulouse (IRIT), Université Toulouse Capitole (UT Capitole), Université de Toulouse (UT)-Université de Toulouse (UT)-Université Toulouse - Jean Jaurès (UT2J), Université de Toulouse (UT)-Centre National de la Recherche Scientifique (CNRS)-Institut National Polytechnique (Toulouse) (Toulouse INP), Université de Toulouse (UT)-Toulouse Mind & Brain Institut (TMBI), Université Toulouse - Jean Jaurès (UT2J), Université de Toulouse (UT)-Université de Toulouse (UT)-Université Toulouse III - Paul Sabatier (UT3), Université de Toulouse (UT)-Université Toulouse Capitole (UT Capitole), and ANR-18-CE46-0012,MCG-Rad,Calcul par Monte-Carlo des forçages radiatifs à l'échelle globale(2018)

Subjects
[PHYS.MECA.THER]Physics [physics]/Mechanics [physics]/Thermics [physics.class-ph], [INFO.INFO-GR]Computer Science [cs]/Graphics [cs.GR]
Abstract

National audience; Nous souhaitons estimer le flux radiatif quittant la Terre intégré sur l'infrarouge thermique, sur toute la surface du globe et sur une période climatique de longue durée. Ce calcul est réputé très difficile à réaliser si on ne fait pas de simplifications de la description fréquentielle, spatiale ou temporelle (e.g. passer d'un modèle raie-par-raie à un modèle de bande, utiliser une discrétisation temporelle plus grossière, etc). Nous montrons que la méthode de Monte Carlo permet d'éviter ces simplifications si on associe les deux idées suivantes : introduire des collisionneurs fictifs pour permettre le suivi de rayon sans connaissance du champ de coefficient d'extinction et échantillonner statistiquement les raies spectrales. Nous montrons qu'il n'est pas plus coûteux de réaliser cette intégration sur un jour ou un mois, sur une colonne atmosphérique ou sur toute la Terre, ou finalement sur une bande étroite fréquentielle ou sur tout le spectre infrarouge.

Published
2022

21. Path-tracing Monte Carlo Libraries for 3D Radiative Transfer in Cloudy Atmospheres

Author

Villefranque, Najda, Fournier, Richard, Couvreux, Fleur, Blanco, Stéphane, Cornet, Céline, Eymet, Vincent, Forest, Vincent, Tregan, Jean-Marc, and Pagès, Nathalie

Subjects
Path-tracing library for flexible implementation of Monte Carlo algorithms in cloudy atmospheres, Null-collision algorithms and hierarchical grids to accelerate ray casting in large volumetric data, [SPI] Engineering Sciences [physics], Insensitivity of radiative transfer computational cost to surface and volume com- plexity
Abstract

Interactions between clouds and radiation are at the root of many difficulties in numeri-cally predicting future weather and climate and in retrieving the state of the atmospherefrom remote sensing observations. The large range of issues related to these interactions,and in particular to three-dimensional interactions, motivated the development of accurateradiative tools able to compute all types of radiative metrics, from monochromatic, localand directional observables, to integrated energetic quantities. In the continuity of thiscommunity effort, we propose here an open-source library for general use in Monte Carloalgorithms. This library is devoted to the acceleration of path-tracing in complex data,typically high-resolution large-domain grounds and clouds. The main algorithmic advancesembedded in the library are those related to the construction and traversal of hierarchicalgrids accelerating the tracing of paths through heterogeneous fields in null-collision (maxi-mum cross-section) algorithms. We show that with these hierarchical grids, the computingtime is only weakly sensitivive to the refinement of the volumetric data. The library is testedwith a rendering algorithm that produces synthetic images of cloud radiances. Two otherexamples are given as illustrations, that are respectively used to analyse the transmissionof solar radiation under a cloud together with its sensitivity to an optical parameter, andto assess a parametrization of 3D radiative effects of clouds.

Published
2022

22. Une estimation exacte du forçage radiatif par la méthode de Monte-Carlo

Author

Nyffenegger-Péré, Yaniss, primary, Bati, Mégane, additional, Blanco, Stéphane, additional, Dufresne, Jean-Louis, additional, El Hafi, Mouna, additional, Eymet, Vincent, additional, Forest, Vincent, additional, Fournier, Richard, additional, Mellado, Nicolas, additional, Mourtaday, Nada, additional, and Paulin, Mathias, additional

Published
2022
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23. Synthèse d'images infrarouges sans calcul préalable du champ de température

Author

Vincent Eymet, Forest Vincent, Benjamin Piaud, Christophe Coustet, Richard Fournier, Stéphane Blanco, Loris Ibarrart, Jean-Marc Tregan, Pascal Lavieille, Cyril Caliot, Mouna El-Hafi, Jean-Jacques Bézian, Rémi Bouchie, Mathieu Galtier, Maxime Roger, Jérémi Dauchet, Olivier Farges, Christophe Péniguel, Isabelle Rupp, Genevière Eymet, Meso-Star, Groupe de Recherche Energétique, Plasmas et Hors Equilibre (LAPLACE-GREPHE), LAboratoire PLasma et Conversion d'Energie (LAPLACE), Centre National de la Recherche Scientifique (CNRS)-Université Toulouse III - Paul Sabatier (UT3), Université Fédérale Toulouse Midi-Pyrénées-Université Fédérale Toulouse Midi-Pyrénées-Institut National Polytechnique (Toulouse) (Toulouse INP), Université Fédérale Toulouse Midi-Pyrénées-Centre National de la Recherche Scientifique (CNRS)-Université Toulouse III - Paul Sabatier (UT3), Université Fédérale Toulouse Midi-Pyrénées, Centre de recherche d'Albi en génie des procédés des solides divisés, de l'énergie et de l'environnement (RAPSODEE), Centre National de la Recherche Scientifique (CNRS)-IMT École nationale supérieure des Mines d'Albi-Carmaux (IMT Mines Albi), Institut Mines-Télécom [Paris] (IMT)-Institut Mines-Télécom [Paris] (IMT), Procédés, Matériaux et Energie Solaire (PROMES), Université de Perpignan Via Domitia (UPVD)-Centre National de la Recherche Scientifique (CNRS), Centre Scientifique et Technique du Bâtiment (CSTB), Centre d'Energétique et de Thermique de Lyon (CETHIL), Centre National de la Recherche Scientifique (CNRS)-Institut National des Sciences Appliquées de Lyon (INSA Lyon), Université de Lyon-Institut National des Sciences Appliquées (INSA)-Université de Lyon-Institut National des Sciences Appliquées (INSA)-Université Claude Bernard Lyon 1 (UCBL), Université de Lyon, Institut Pascal (IP), SIGMA Clermont (SIGMA Clermont)-Université Clermont Auvergne [2017-2020] (UCA [2017-2020])-Centre National de la Recherche Scientifique (CNRS), Laboratoire Énergies et Mécanique Théorique et Appliquée (LEMTA ), Université de Lorraine (UL)-Centre National de la Recherche Scientifique (CNRS), Mécanique des Fluides, Energies et Environnement (EDF R&D MFEE), EDF R&D (EDF R&D), EDF (EDF)-EDF (EDF), Lycée Victor Hugo Gaillac, Méso-Star, Université Toulouse III - Paul Sabatier (UT3), Université de Toulouse (UT)-Université de Toulouse (UT)-Centre National de la Recherche Scientifique (CNRS)-Institut National Polytechnique (Toulouse) (Toulouse INP), Université de Toulouse (UT)-Université Toulouse III - Paul Sabatier (UT3), Université de Toulouse (UT), Université Claude Bernard Lyon 1 (UCBL), Université de Lyon-Université de Lyon-Institut National des Sciences Appliquées de Lyon (INSA Lyon), Université de Lyon-Institut National des Sciences Appliquées (INSA)-Institut National des Sciences Appliquées (INSA)-Centre National de la Recherche Scientifique (CNRS), and Farges, Olivier

Subjects
[SPI.MECA.THER]Engineering Sciences [physics]/Mechanics [physics.med-ph]/Thermics [physics.class-ph], [INFO.INFO-MO] Computer Science [cs]/Modeling and Simulation, [INFO.INFO-MO]Computer Science [cs]/Modeling and Simulation, [SPI.MECA.THER] Engineering Sciences [physics]/Mechanics [physics.med-ph]/Thermics [physics.class-ph]
Abstract

National audience; Nous presentons un ensemble d’algorithmes statistiques permettant d’effectuer le rendu d’une image thermique, en régime instationnaire, dans une scène quelconque. Simuler le signal reçu par chaque pixel de la camera consiste à propager les sources thermiques (conditions aux limites et initiales) par les phenomènes de conduction, convection et rayonnement. La technique ne nécessite pas un calcul préalable du champ de température en tout point de la scène et en tout temps. Un exemple en geométrie complexe est présenté, et qualitativement comparé à une prise de vue.

Published
2019

24. Combined conductive-convective-radiative heat transfer in complex geometry using the Monte Carlo method: application to solar receivers

Author

Loris Ibarrart, Cyril Caliot, Mouna El HAFI, Fournier, Richard A., Stéphane Blanco, Sébastien Dutour, Jeremi Dauchet, Jean-Marc Tregan, Vincent Eymet, Forest Vincent, Centre de recherche d'Albi en génie des procédés des solides divisés, de l'énergie et de l'environnement (RAPSODEE), Centre National de la Recherche Scientifique (CNRS)-IMT École nationale supérieure des Mines d'Albi-Carmaux (IMT Mines Albi), Institut Mines-Télécom [Paris] (IMT)-Institut Mines-Télécom [Paris] (IMT), Procédés, Matériaux et Energie Solaire (PROMES), Université de Perpignan Via Domitia (UPVD)-Centre National de la Recherche Scientifique (CNRS), Groupe de Recherche Energétique, Plasmas et Hors Equilibre (LAPLACE-GREPHE), LAboratoire PLasma et Conversion d'Energie (LAPLACE), Centre National de la Recherche Scientifique (CNRS)-Université Toulouse III - Paul Sabatier (UT3), Université Fédérale Toulouse Midi-Pyrénées-Université Fédérale Toulouse Midi-Pyrénées-Institut National Polytechnique (Toulouse) (Toulouse INP), Université Fédérale Toulouse Midi-Pyrénées-Centre National de la Recherche Scientifique (CNRS)-Université Toulouse III - Paul Sabatier (UT3), Université Fédérale Toulouse Midi-Pyrénées, Institut Pascal (IP), SIGMA Clermont (SIGMA Clermont)-Université Clermont Auvergne [2017-2020] (UCA [2017-2020])-Centre National de la Recherche Scientifique (CNRS), Meso-Star, THE HEAT AND MASS TRANSFER SOCIETY OF CHINA, TSINGHUA UNIVERSITY, Université Toulouse III - Paul Sabatier (UT3), Université de Toulouse (UT)-Université de Toulouse (UT)-Centre National de la Recherche Scientifique (CNRS)-Institut National Polytechnique (Toulouse) (Toulouse INP), Université de Toulouse (UT)-Université Toulouse III - Paul Sabatier (UT3), Université de Toulouse (UT), Méso-Star, Université Fédérale Toulouse Midi-Pyrénées-Université Fédérale Toulouse Midi-Pyrénées-Centre National de la Recherche Scientifique (CNRS)-Institut National Polytechnique (Toulouse) (Toulouse INP), Université Fédérale Toulouse Midi-Pyrénées-Université Toulouse III - Paul Sabatier (UT3), and SIGMA Clermont (SIGMA Clermont)-Centre National de la Recherche Scientifique (CNRS)-Université Clermont Auvergne [2017-2020] (UCA [2017-2020])

Subjects
[SPI]Engineering Sciences [physics], Radiation, Computational methods, Porous media, Conduction, Convection, Monte Carlo
Abstract

International audience; Deterministic methods are commonly used to solve coupled conductive-convective-radiative systems in threedimensional geometries (3D). With the increasing amount and accuracy of data available, and growing complexity of systems studied, these methods have to deal with endless increases in computation times. This article presents a stochastic method for the simulation of the heat balance equation in solids and fluids with known velocity fields, as well as coupled surface to surface radiative transfers. The construction of the corresponding algorithm is comprehensively detailed and results are compared to deterministic simulations. The presented method uses a Monte Carlo approach and is shown to preserve short computation times for complex geometries.

Published
2018

25. The fabrication and assembly of the beam source for the SPIDER experiment

Author

Masiello Antonio, Ceracchi Andrea, Faso Diego, Forest Vincent, Grenier Jean Marc, Lievin Christophe, Geli Francois, Graceffa Joseph, Marcuzzi Diego, Pavei Mauro, Zaccaria Pierluigi, Corniani Giorgio, Rizzetto Dario, Busch Michael, and Szcepaniak Bernd

Subjects
ITER, Neutral Beam Test Facility, NBTF, SPIDER
Abstract

The ITER Heating Neutral Beam injector will be equipped with a beam source that will provide a negative beam of 40A (H2 or D2). The R&D activities undertaken in Europe to pursue this challenging goal comprise three experiments: - ELISE the half size ion source experiment operating in IPP Garching - SPIDER the full size ion source experiment at Neutral Beam Test Facility (NBTF) site in Padua - MITICA the full size full energy ITER injector prototype being also established at the NBTF The procurement of the beam source for SPIDER started in October 2012, when a contract was signed between Fusion for Energy and Thales Electron Devices (as group leader of a Consortium created with CECOM Srl, Galvano-T GmbH and Zanon SpA). The contract, still on-going at present stage, has been mostly completed in October 2017 with the delivery of the SPIDER beam source at the NBTF site in Padova Italy. A review of the fabrication of the main parts and of the aspects of their assembly will be given with a focus on the difficulties encountered and the solutions adopted. The SPIDER beam source is in fact the `rst ITER full-size source and many of the components had never been manufactured before. Changes in the design induced by the results of the `rst experiment on the ELISE facility will be also described. In the assembly phases of the project, some issues hampered the timely completion of the activities calling for delicate evaluations and the need of taking quick decisions. The paper will provide an overview of the risk management performed in support of the decision taken. Finally, the description of the modi`cations adopted for the MITICA beam source that were identi `ed during the manufacturing and assembly of the SPIDER beam source will be described in detail.

Published
2018

27. Robust object-based algorithms for direct shadow simulation

Author

Forest, Vincent and Forest, Vincent

Abstract

En informatique graphique, les algorithmes de générations d'ombres évaluent la quantité de lumière directement perçue par une environnement virtuel. Calculer précisément des ombres est cependant coûteux en temps de calcul. Dans cette dissertation, nous présentons un nouveau système basé objet robuste, qui permet de calculer des ombres réalistes sur des scènes dynamiques et ce en temps interactif. Nos contributions incluent notamment le développement de nouveaux algorithmes de génération d'ombres douces ainsi que leur mise en oeuvre efficace sur processeur graphique. Nous commençons par formaliser la problématique du calcul d'ombres directes. Tout d'abord, nous définissons ce que sont les ombres directes dans le contexte général du transport de la lumière. Nous étudions ensuite les techniques interactives qui génèrent des ombres directes. Suite à cette étude nous montrons que mêmes les algorithmes dit physiquement réalistes se reposent sur des approximations. Nous mettons également en avant, que malgré leur contraintes géométriques, les algorithmes d'ombres basées objet sont un bon point de départ pour résoudre notre problématique de génération efficace et robuste d'ombres directes. Basé sur cette observation, nous étudions alors le système basé objet existant et mettons en avant ses problèmes de robustesse. Nous proposons une nouvelle technique qui améliore la qualité des ombres générées par ce système en lui ajoutant une étape de mélange de pénombres. Malgré des propriétés et des résultats convaincants, les limitations théoriques et de mise en oeuvre limite la qualité générale et les performances de cet algorithme. Nous présentons ensuite un nouvel algorithme d'ombres basées objet. Cet algorithme combine l'efficacité de l'approche basée objet temps réel avec la précision de sa généralisation au rendu hors ligne. Notre algorithme repose sur l'évaluation locale du nombre d'objets entre deux points : la complexité de profondeur. Nous décrivons comment nous utilisons c, Direct shadow algorithms generate shadows by simulating the direct lighting interaction in a virtual environment. The main challenge with the accurate direct shadow problematic is its computational cost. In this dissertation, we develop a new robust object-based shadow framework that provides realistic shadows at interactive frame rate on dynamic scenes. Our contributions include new robust object-based soft shadow algorithms and efficient interactive implementations. We start, by formalizing the direct shadow problematic. Following the light transport problematic, we first formalize what are robust direct shadows. We then study existing interactive direct shadow techniques and outline that the real time direct shadow simulation remains an open problem. We show that even the so called physically plausible soft shadow algorithms still rely on approximations. Nevertheless we exhibit that, despite their geometric constraints, object-based approaches seems well suited when targeting accurate solutions. Starting from the previous analyze, we investigate the existing object-based shadow framework and discuss about its robustness issues. We propose a new technique that drastically improve the resulting shadow quality by improving this framework with a penumbra blending stage. We present a practical implementation of this approach. From the obtained results, we outline that, despite desirable properties, the inherent theoretical and implementation limitations reduce the overall quality and performances of the proposed algorithm. We then present a new object-based soft shadow algorithm. It merges the efficiency of the real time object-based shadows with the accuracy of its offline generalization. The proposed algorithm lies onto a new local evaluation of the number of occluders between $two$ points (\ie{} the depth complexity). We describe how we use this algorithm to sample the depth complexity between any visible receiver and the light source. From this information, we com

Published
2008

33. Denmark.

Author

Forest, Vincent

Subjects
DANISH politics & government, 1972-, DANISH economy, 1945-, ELECTIONS, BUDGET surpluses, PRICE inflation, GROSS domestic product, FOREIGN exchange rates
Abstract

The report presents an outlook for political and economic conditions in Denmark from 2013 to 2017. According to the Economist Intelligence Unit Ltd., the risk of an early election has increased because of the falling approval rating of the minority coalition. The firm believes that the budget will not return to surplus during the period. In addition, the firm forecasts the performance of the country's economic indicators, including inflation, gross domestic product (GDP) and exchange rates.

Published
2013

34. Denmark.

Author

Forest, Vincent

Subjects
POLITICAL forecasting, DANISH politics & government, 1972-, ELECTIONS, POLITICAL parties, ECONOMIC forecasting, DANISH economy, 1945-, GROSS domestic product
Abstract

A country report for Denmark as of December 2012 is presented. During the 2013-17 forecast period, there is an increased risk of an early election amid the declining poll ratings of the minority coalition of the Social Democrats, Socialist People's Party, and Social Liberal Party. Denmark's budget is not expected to return to surplus during the 2013-17 period. It expects a moderate rise in gross domestic product (GDP) growth after 2012.

Published
2012

38. Wave-scattering processes: path-integrals designed for the numerical handling of complex geometries.

Author

Dauchet J, Charon J, Blanco S, Brunel L, Cornet JF, Coustet C, El Hafi M, Eymet V, Forest V, Fournier R, Gros F, Piaud B, Terrée G, and Vourc'h T

Abstract

Relying on Feynman-Kac path-integral methodology, we present a new statistical perspective on wave single-scattering by complex three-dimensional objects. The approach is implemented on three models-Schiff approximation, Born approximation, and rigorous Born series-and familiar interpretative difficulties such as the analysis of moments over scatterer distributions (size, orientation, shape, etc.) are addressed. In terms of the computational contribution, we show that commonly recognized features of the Monte Carlo method with respect to geometric complexity can now be available when solving electromagnetic scattering.

Published
2023
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