Publications HAL

2022

Communication dans un congrès

titre: Wildfires Physics and Modelling
auteur: Sofiane Meradji, Dominique Morvan, Gilbert Accary
article: International Conference on Materials & Energy 2022, May 2022, Baku, Azerbaijan
typdoc: Communication dans un congrès
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titre: Numerical Study of Junction Fires on Sloped Terrain for Grassland Vegetation
auteur: Jacky Fayad, Gilbert Accary, Duncan Sutherland, Sofiane Meradji, Nicolas Frangieh, Khaled Moinuddin, Dominique Morvan, François Joseph Chatelon, Jean-Louis Rossi
article: Third International Conference on Fire Behavior and Risk (ICFBR2022 ), May 2022, Alghero, Italy. pp.112, ⟨10.3390/environsciproc2022017112⟩
typdoc: Communication dans un congrès
DOI: DOI : 10.3390/environsciproc2022017112
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Chapitre d'ouvrage

titre: Physics-based modelling of junction fires: Sensitivity and Validation studies
auteur: Ahmad Hassan, Gilbert Accary, Duncan Sutherland, Sofiane Meradji, Khalid Moinuddin
article: Advances in Forest Fire Research 2022, 1.ª Edição, Imprensa da Universidade de Coimbra, pp.315-322, 2022, ⟨10.14195/978-989-26-2298-9_50⟩
resume: The process of modelling and replicating extreme fire behaviour like junction fire is essential for understanding the phenomena associated with extreme fires. Numerical simulations of junction fires, replicating laboratory-scale experiments, with no imposed wind, were performed for a shrub fuel bed with slopes ranging from 0Â° to 30Â°. The simulations of junction fires were conducted for two junction angles 30Â° and 45Â°. For each scenario, the sensitivity to a range of numerical and physical parameters was investigated. The rate of spread (ROS) is a key parameter for assessing risks from vegetation fires. Experimental spreading junction fires, conducted at laboratory scale at Coimbra University (Portugal), were simulated using FIRESTAR3D - a three-dimensional physics-based fire model. To ensure the robustness of simulations, sensitivity analyses were carried out by varying the grid resolution, domain size, different fuel characteristics, as well as some of the thermo-physical parameters. The corresponding simulations were carried out using a single and two descriptions levels of the shrub: the vegetation was represented using only one cylindrical-shaped solid-fuel type (excelsior fuel using the characteristic parameters for Erica shrub), or two fuel by adding the contribution of twigs of various diameters up to 6 mm while keeping the same packing ratio. Finally, the validation of FIRESTAR3D simulations was achieved through the comparison of predicted and measured ROS values. The experimental trends of the compared quantities were well reproduced by the simulations. Accelerating and decelerating propagation phases were observed in all simulations, with a dependence on the slope angle, while the maximum rate of spread depends critically on the junction angle. As it was the case of other wildfires simulated by FIRESTAR3D, it was found that this fully-physical model is capable of simulating junction fire propagation. There are several processes associated with the development of a junction fire behaviour, in which dramatic changes in fire behaviour can occur with little change in various fuel, weather and topographical parameters. In a subsequent study, we aim to develop an understanding of junction fire behaviour taking into account essential parameters that affect the behaviour, namely: slope, junction angle, and driving wind velocity.
typdoc: Chapitre d'ouvrage
DOI: DOI : 10.14195/978-989-26-2298-9_50
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2021

Article dans une revue

titre: Numerical study of the moisture content threshold under prescribed burning conditions
auteur: Carmen Awad, Nicolas Frangieh, Thierry Marcelli, Gilbert Accary, Dominique Morvan, Sofiane Meradji, François Joseph Chatelon, Jean Louis Rossi
article: Fire Safety Journal, 2021, pp.103324. ⟨10.1016/j.firesaf.2021.103324⟩
resume: The safety during prescribed burnings could be achieved by conducting these operations under marginal conditions of fire propagation. This type of fire can or cannot propagate on account of small deviations of the burning conditions, mainly the wind speed, the fuel load, and the fuel moisture-content. In this context, numerical simulations of grassland fires were conducted under marginal conditions in order to relate the moisturecontent threshold of propagation success to the wind speed and the fuel load. The simulations were conducted using FireStar2D, a complete physical 2D fire simulator based on a multiphase modelling approach. The 10 mopen wind speed ranged from 0 to 10 m/s and the fuel load varied from 0.1 kg/m 2 to 0.7 kg/m 2. The effects of wind speed and fuel moisture-content on the fire behaviour and on the flame parameters are discussed. The results show that the moisture threshold increases with the fuel load until it reaches a value beyond which there is no dependence. A similar dependence of the moisture threshold on the wind speed is also observed. Finally, empirical formulae were constructed to relate the fuel moisture content threshold to the wind speed and the fuel loading implicitly through Byram's convective number.
typdoc: Article dans une revue
DOI: DOI : 10.1016/j.firesaf.2021.103324
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titre: Numerical study of the moisture content threshold under prescribed burning conditions
auteur: Carmen Awad, Nicolas Frangieh, Thierry Marcelli, Gilbert Accary, Dominique Morvan, Sofiane Meradji, François Joseph Chatelon, Jean Louis Rossi
article: Fire Safety Journal, 2021, pp.103324. ⟨10.1016/j.firesaf.2021.103324⟩
typdoc: Article dans une revue
DOI: DOI : 10.1016/j.firesaf.2021.103324
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titre: Parallel modeling of wildfires using efficient solvers for ill-conditioned linear systems
auteur: Oleg Bessonov, Sofiane Meradji
article: Journal of Supercomputing, 2021
typdoc: Article dans une revue
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Communication dans un congrès

titre: Experimental and numerical study of high intensity prescribed fire across Corsican Genista salzmannii vegetation.
auteur: Jacky Fayad, Lucile Rossi, Nicolas Frangieh, Carmen Awad, Gilbert Accary, François-Joseph Chatelon, F. Morandini, Thierry Marcelli, Valérie Leroy-Cancellieri, Dominique Cancellieri, Dominique Morvan, Antoine Pieri, Planelles Gilles, Costantini René, Sofiane Meradji, Jean Louis Rossi
article: American Geophysical Union Fall Meeting, Dec 2021, New Orleans LA, United States
typdoc: Communication dans un congrès
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titre: Junction fires on sloped terrain
auteur: Jacky Fayad, Gilbert Accary, David Sutherland, Nicolas Frangieh, Sofiane Meradji, Khalid Moinuddin, Dominique Morvan, Jean-Louis Rossi
article: 9th Int. Fire Ecol. Manag. Congr.,, Nov 2021, Tucson, Arizona, United States
typdoc: Communication dans un congrès
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2020

Article dans une revue

titre: Wildfires front dynamics: 3D structures and intensity at small and large scales
auteur: Nicolas Frangieh, Gilbert Accary, Dominique Morvan, Sofiane Meradji, Oleg Bessonov
article: Combustion and Flame, 2020, 211, pp.54-67. ⟨10.1016/j.combustflame.2019.09.017⟩
resume: The 3D structure of a fire front propagating through a homogeneous porous solid-fuel layer was studied numerically at laboratory and field scales. At laboratory scale, wind-tunnel fires propagating through laser-cut cardboard fuel were numerically reproduced, while at field scale, simulations of grassland fires with quasi-infinite fire front were carried out for different wind speeds. These simulations were performed using FIRESTAR3D, based on a multiphase formulation that includes the main physical phenomena governing fire behavior. An unsteady RANS approach and a Large Eddy Simulation (LES) approach were used to simulate the reactive turbulent flow, whereas turbulent combustion was modeled using Eddy Dissipation Concept (EDC). Unlike other 3D wildfire tools available in the community, such as FIRETEC and WFDS, the model is based on an implicit, low-Mach number resolution of the governing equations, and makes no empirical assumptions in the resolution of the radiative transfer equation. The comparison with the experimental data concerned mainly the Rate of Spread (ROS) of fire, the fireline intensity, the flame-zone depth, and the wavelength characterizing the crest-and-trough structure of the fire front along the transverse direction. Particular attention was drawn to the similitude in the fire front dynamics between small and large scales. In order to highlight the physical mechanisms responsible for this dynamics, a dimensional analysis was carried out by introducing Byram's convection number N-C based on the fireline intensity and Froude's numbers Fr based on the characteristic wavelength of the fire-front structure. The analysis shows that all the results (wind-tunnel fires and grassland fires, experimental and numerical) collapsed on a single scaling law in the form Fr = N-C(-)2/3.
typdoc: Article dans une revue
DOI: DOI : 10.1016/j.combustflame.2019.09.017
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titre: Physics-Based Simulations of Flow and Fire Development Downstream of a Canopy
auteur: Gilbert Accary, Duncan Sutherland, Nicolas Frangieh, Khalid Moinuddin, Ibrahim Shamseddine, Sofiane Meradji, Dominique Morvan
article: Atmosphere, 2020, 11 (7), pp.683. ⟨10.3390/atmos11070683⟩
resume: The behavior of a grassland fire propagating downstream of a forest canopy has been simulated numerically using the fully physics-based wildfire model FIRESTAR3D. This configuration reproduces quite accurately the situation encountered when a wildfire spreads from a forest to an open grassland, as can be the case in a fuel break or a clearing, or during a prescribed burning operation. One of the objectives of this study was to evaluate the impact of the presence of a canopy upstream of a grassfire, especially the modifications of the local wind conditions before and inside a clearing or a fuel break. The knowledge of this kind of information constitutes a major element in improving the safety conditions of forest managers and firefighters in charge of firefighting or prescribed burning operations in such configurations. Another objective was to study the behavior of the fire under realistic turbulent flow conditions, i.e., flow resulting from the interaction between an atmospheric boundary layer (ABL) with a surrounding canopy. Therefore, the study was divided into two phases. The first phase consisted of generating an ABL/canopy turbulent flow above a pine forest (10 m high, 200 m long) using periodic boundary conditions along the streamwise direction. Large Eddy Simulations (LES) were carried out for a sufficiently long time to achieve a quasi-fully developed turbulence. The second phase consisted of simulating the propagation of a surface fire through a grassland, bordered upstream by a forest section (having the same characteristics used for the first step), while imposing the turbulent flow obtained from the first step as a dynamic inlet condition to the domain. The simulations were carried out for a wind speed that ranged between 1 and 12 m/s; these values have allowed the simulations to cover the two regimes of propagation of surfaces fires, namely plume-dominated and wind-driven fires.
typdoc: Article dans une revue
DOI: DOI : 10.3390/atmos11070683
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2019

Chapitre d'ouvrage

titre: Efficient Parallel Solvers for the FireStar3D Wildfire Numerical Simulation Model
auteur: Oleg Bessonov, Sofiane Meradji
article: Malyshkin V. (eds) Parallel Computing Technologies. PaCT 2019. Lecture Notes in Computer Science, vol 11657. Springer, Cham, pp.140-150, 2019, 978-3-030-25635-7. ⟨10.1007/978-3-030-25636-4_11⟩
resume: This paper presents efficient parallel methods for solving ill-conditioned linear systems arising in fluid dynamics problems. The first method is based on the Modified LU decomposition, applied as a preconditioner to the Conjugate gradient algorithm. Parallelization of this method is based on the use of nested twisted factorization. Another method is based on a highly parallel Algebraic multigrid algorithm with a new smoother developed for anisotropic grids. Performance comparisons demonstrate superiority of new methods over commonly used variants of the Conjugate gradient method.
typdoc: Chapitre d'ouvrage
DOI: DOI : 10.1007/978-3-030-25636-4_11
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2018

Article dans une revue

titre: Numerical simulation of grassland fires behavior using an implicit physical multiphase model
auteur: Nicolas Frangieh, Dominique Morvan, Sofiane Meradji, Gilbert Accary, Oleg Bessonov
article: Fire Safety Journal, 2018, 102, pp.37-47. ⟨10.1016/j.firesaf.2018.06.004⟩
resume: 12 This study reports 3D numerical simulations of the ignition and the propagation of 13 grassland fires. The mathematical model is based on a multiphase formulation and on a 14 homogenization approach that consists in averaging the conservation equations (mass, 15 momentum, energy …) governing the evolution of variables representing the state of the 16 vegetation/atmosphere system, inside a control volume containing both the solid-17 vegetation phase and the surrounding gaseous phase. This preliminary operation results 18 in the introduction of source/sink additional terms representing the interaction between 19 the gaseous phase and the solid-fuel particles. This study was conducted at large scale in 20 grassland because it represents the scale at which the behavior of the fire front presents 21 most similarities with full scale wildfires and also because of the existence of a large 22 number of relatively well controlled experiments performed in Australia and in the 23 United States. The simulations were performed for a tall grass, on a flat terrain, and for 24 six values of the 10-m open wind speed ranged between 1 and 12 m/s. The results are in 25 fairly good agreement with experimental data, with the predictions of operational 26 empirical and semi-empirical models, such as the McArthur model (MK5) in Australia and 27 the Rothermel model (BEHAVE) in USA, as well as with the predictions of other fully 3D 28 physical fire models (FIRETEC and WFDS). The comparison with the literature was 29 mainly based on the estimation of the rate of fire spread (ROS) and of the fire intensity, 30 as well as on the analysis of the fire-front shape. 31 32
typdoc: Article dans une revue
DOI: DOI : 10.1016/j.firesaf.2018.06.004
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titre: A 3D physical model to study the behavior of vegetation fires at laboratory scale
auteur: Dominique Morvan, Gilbert Accary, Sofiane Meradji, Nicolas Frangieh, Oleg Bessonov
article: Fire Safety Journal, 2018, 101, pp.39-52. ⟨10.1016/j.firesaf.2018.08.011⟩
resume: A 3D multi-physical model referred to as “FireStar3D” has been developed in order to predict the behavior of wildfires at a local scale (<500 m). In the continuity of a previous work limited to 2D configurations, this model consists of solving the conservation equations of the coupled system composed of the vegetation and the surrounding gaseous medium. In particular, the model is able to account explicitly for all the mechanisms of degradation of the vegetation (by drying, pyrolysis, and heterogeneous combustion) and the various interactions between the gas mixture (ambient air + pyrolysis and combustion products) and the vegetation cover such as drag force, heat transfer by convection and radiation, and mass transfer. Compared to previous works, some new features were introduced in the modeling of the surface combustion of charcoal, the calculation of the heat transfer coefficient between the solid fuel particles and the surrounding atmosphere, and many improvements were brought to the numerical method to enable affordable 3D simulations. The partial validation of the model was based on some comparisons with experimental data collected at small scale fires carried out in the Missoula Fire Sciences Lab's wind tunnel, through various solid-fuel layers and in well controlled conditions. A relative good agreement was obtained for most of the simulations that were conducted. A parametric study of the dependence of the rate of spread on the wind speed and on the fuelbed characteristics is presented.
typdoc: Article dans une revue
DOI: DOI : 10.1016/j.firesaf.2018.08.011
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Communication dans un congrès

titre: Front's dynamics of quasi-infinite grassland fires
auteur: Nicolas Frangieh, Gilbert Accary, Sofiane Meradji, Dominique Morvan
article: 8th International Conference on Forest Fire Research, Nov 2018, Coimbra, Portugal
resume: Numerical simulations of grassland fires were carried out to study the effects of the wind speed on the dynamics of the fire front. This study was performed using a detailed physical model based on a multiphase formulation, consisting in solving the balance equations (mass, momentum, energy ...) governing the behavior of the coupled system formed by the vegetation layer and the surrounding atmosphere. The objective of this study is to focus on the 3D interactions between a quasi-infinite fire front propagating through a homogeneous vegetation layer (a grassland) and an atmospheric boundary layer flow representing an idealized wind flow. The behavior of a surface fire results from the competition between the buoyant force of the thermal plume and the inertial force of the wind. In 3D, the interaction between these two forces is at the origin of the structuration of the fire front as a succession of peaks and troughs that modify the flames dynamics in a manner different to what can be observed in a simplified 2D assumption. To reproduce a quasi-infinite fire front, the numerical simulations were carried out using periodic boundary conditions along the two lateral sides of the computational domain. The numerical results highlights the 3D structuration of the fire both vertically and horizontally, and the significant effect of an increase of the wind velocity on the rate of spread (ROS) and on the fire intensity. Results also show that the correlation between Froude’s number (based on the fire-front structures characteristic-wavelength) and Byram’s number is the same at small scale (litter fires) and at large scale (grassland fires).
typdoc: Communication dans un congrès
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2017

Communication dans un congrès

titre: Inlet and Outlet Open Boundary Conditions for Incompressible Navier-Stokes Equations
auteur: Cedric Galusinski, C. Mazoyer, Sofiane Meradji, A. Molcard, Yann Ourmieres
article: Topical Problems of Fluid Mechanics 2017, Jan 2017, Prague, Czech Republic. ⟨10.14311/TPFM.2017.018⟩
resume: Flow simulation models often contain open boundaries in order to avoid computations on too large or infinite domains. The open boundary conditions partially drives the flow and the influence of the outer domain has to be taken into account on such boundaries. " Free " open boundary conditions are then essential to the model. The goal of this work is to introduce a new open boundary condition, adapted both for inlet and outlet, parametrized and driven by simple informations such as flow rate.
typdoc: Communication dans un congrès
DOI: DOI : 10.14311/TPFM.2017.018
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2016

Proceedings/Recueil des communications

titre: Numerical Simulation of Grassland-Fires Behavior Using FireStar3D Model
auteur: Sofiane Meradji, Gilbert Accary, Dominique Morvan, Oleg Bessonov, Dominique Fougere
article: Topical Problems of Fluid Mechanics, Feb 2016, Prague, Czech Republic. , pp.254, 2016, In Proceedings Topical Problems of Fluid Mechanics 2016, 978-80-87012-58-1. ⟨10.14311/TPFM.2016.018⟩
resume: This study reports 3D numerical simulations of the ignition and the propagation of grassland fires. The mathematical model consists in solving the conservation equations governing the behavior of the coupled system formed by the vegetation and the ambient atmosphere. Based on a finite volume discretization, the computation code is parallelized using OpenMP directives and had been the subject of numerous validations. the model was previously tested on small scale in case of homogeneous litter fires; in this study it is proposed to test it on larger scale in case of grassland fires. the results are in fairly agreement with experimental data, with predictions of operational empirical-models developed in Australia (MK5) and in the USA (BEHAVE), as well as with predictions of physical models (FIRETEC, WFDS, FireStar2D). The comparison with the literature is based on the estimation of the rate of fire spread (ROS) and the analysis of the fire-front shape.
typdoc: Proceedings/Recueil des communications
DOI: DOI : 10.14311/TPFM.2016.018
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2015

Communication dans un congrès

titre: Hypobiose estivale précoce des nématodes trichostrongles de la caillette des agneaux dans une zone steppique du nord-est algérien
auteur: Sofiane Meradji, Jacques J. Cabaret, Bourhane Bentounsi
article: 2. Journée de Parasitologie, Université Hadj Lakhdar de Batna. DZA., Oct 2015, Batna, Algérie
typdoc: Communication dans un congrès
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Proceedings/Recueil des communications

titre: FireStar3D : Modèle tridimensionnel pour la prédiction de la propagation d'un feu en milieu naturel
auteur: Sofiane Meradji, Gilbert Accary, Dominique Morvan, Oleg Bessonov, Dominique Fougere
article: 17èmes Journées Internationales de Thermique (JITH 2015), Oct 2015, Marseille, France. 2015
resume: Cette étude concerne la modélisation et la simulation numérique de l’ignition et de la propagation d’un feu de prairie. La formulation mathématique repose sur une approche multiphasique, construite à partir des équations de conservation gouvernant l’état du système couplé formé par la végétation et l’atmosphère ambiant. Le code de calcul développé dans le cadre de ce travail, reposant sur une méthode de discrétisation de type volumes finis, est parallélisé à l'aide de directives OpenMP et a fait l'objet de nombreuses validations. Le modèle implémenté a été préalablement testé à petite échelle, sur des feux de litière homogène et on se propose de le tester à plus grande échelle. Les résultats préliminaires, portant sur l'estimation de la vitesse de propagation du front de flamme (ROS) et sur l’analyse de la forme du front de flamme, sont en assez bon accord avec les données expérimentales de la littérature, les prédictions des modèles empiriques opérationnels développés en Australie (MK5) et aux Etats-Unis (BEHAVE) et les prédictions des modèles physiques (FIRETEC, WFDS, FireStar2D).
typdoc: Proceedings/Recueil des communications
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2014

Proceedings/Recueil des communications

titre: FireStar3D: 3D finite volume model for the prediction of wildfires
auteur: Gilbert Accary, Sofiane Meradji, Dominique Morvan, Oleg Bessonov, Dominique Fougere
article: VII International Conference on Forest Fire Research, Coimbra, Portugal. , 2014, Advances in forest fires research, 978-989-26-0884-6 (PDF). ⟨10.14195/978-989-26-0884-6_27⟩
resume: A fully-physical wildfire model was used to simulate a confined fire in a wind tunnel. A preliminary study was carried out in the case of homogeneous fuel bed to evaluate the potential of the model to predict fire behavior. The obtained results were analyzed in terms of fire front rate of spread (ROS) and shape, for different wind velocities and fuel moisture content values and compared with experimental data from the literature (measurements and empirical correlations).
typdoc: Proceedings/Recueil des communications
DOI: DOI : 10.14195/978-989-26-0884-6_27
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2013

Article dans une revue

titre: Interaction between head fire and backfire in grasslands
auteur: Dominique Morvan, Sofiane Meradji, William Mell
article: Fire Safety Journal, 2013, 58, pp.195-203. ⟨10.1016/j.firesaf.2013.01.027⟩
resume: This paper deals with 3D numerical simulations of two fires fronts (head and backfire) propagating simultaneously through a grassland fuel. The simulations were carried out using a "fully" physical and three-dimensional fire model (namely WFDS). One of the objectives of this work, was to evaluate the potential for fully physical fire model to simulate the interactions between two fire fronts (a head fire and a backfire), in conditions similar to those encountered during suppression fire operations. A set of numerical simulations was first carried out for standalone head fires propagating through grasslands on a flat terrain and for various wind conditions ranging between 1 and 10 m/s. These results were compared with experimental data and numerical results from the literature. The same calculations were then repeated, with a backfire ignited at the downwind side of the plot. The numerical results highlighted that, for these particular conditions, head fire and backfire can interact, mainly, via two mechanisms: - at relatively large distances (greater than 10 m) the head fire acts on backfire as a screen and reduces the direct action of the wind flow on the backfire, - at relative small distances (nearly equal to 10 m) the gas flow (entrainment) generated in the vicinity of the head fire promotes the aspiration of the backfire towards the main fire front.
typdoc: Article dans une revue
DOI: DOI : 10.1016/j.firesaf.2013.01.027
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titre: Numerical simulation of coherent turbulent structures and of passive scalar dispersion in a canopy sub-layer
auteur: K. Gavrilov, Dominique Morvan, Gilbert Accary, Dimitry Lyubimov, Sofiane Meradji
article: Computers and Fluids, 2013, LES of turbulence aeroacoustics and combustion, 78, pp.54-62. ⟨10.1016/j.compfluid.2012.08.021⟩
resume: This study deals with the problem of turbulent atmospheric boundary-layer flow over a forest canopy. Numerous previous works showed that this flow presents more similarities with a mixing-layer flow than with the standard boundary-layer flow. In this paper, this problem was studied for homogeneous canopies, using large eddy simulation (LES). The numerical results reproduced correctly the various steps of development of this flow: the appearance of a first generation of coherent structures resulting from the development of a primary Kelvin-Helmholtz instability, the reorganization of these structures, by vortex pairing and kinking, the development of a secondary instability and the formation of horseshoe vortices. Then, the process of transport of a passive scalar from a forest canopy into a clear atmosphere was studied in two cases, i.e., when the passive scalar concentration at the surface foliage is either constant or time-varying. Even though this small difference has little influence on the concentration patterns, the results showed that it can significantly affect the concentration magnitude as well as the dynamics of the total concentration in the atmosphere.
typdoc: Article dans une revue
DOI: DOI : 10.1016/j.compfluid.2012.08.021
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Ouvrages

titre: Admixture transport model for atmospheric boundary layer flow over forest canopy
auteur: Konstantin Gavrilov, Dmitri Lyubimov, Dominique Morvan, Gilbert Accary, Sofiane Meradji
article: N. I. Lobachevsky Bulletin de l'Université de Ninji-Novgorod, 1 (3), pp.244-252, 2013, La Modélisation Mathématique: Contôle Optimal
typdoc: Ouvrages
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2011

Article dans une revue

titre: Numerical modeling of coherent structures attendant on impurity propagation in the atmospheric boundary layer over a forest canopy
auteur: K. Gavrilov, Dominique Morvan, Gilbert Accary, D.V. Lyubimov, Sofiane Meradji, Oleg A. Bessonov
article: Fluid Dynamics / Izvestiya Akademii Nauk - Mekhanika Zhidkosti i Gaza, 2011, 46 (1), pp.138-147. ⟨10.1134/S0015462811010169⟩
resume: Three-dimensional large eddy simulation is used to solve the problem for a homogeneous forest canopy. The development of the Kelvin-Helmholtz instability above the canopy leads to the formation of coherent structures in the atmosphere flow, which are reproduced in the calculations. The statistical characteristics of the flow obtained from the numerical modeling are compared with experimental data. The passive admixture transfer from the canopy to the clean atmosphere is studied for two cases, namely, for constant and variable coupled concentration of the impurity in the canopy.
typdoc: Article dans une revue
DOI: DOI : 10.1134/S0015462811010169
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titre: Numerical simulation of coherent structures over plant canopy
auteur: Konstantin Gavrilov, Gilbert Accary, Dominique Morvan, Dimitry Lyubimov, Sofiane Meradji, Oleg A. Bessonov
article: Flow, Turbulence and Combustion, 2011, 86 (1), pp.89-111. ⟨10.1007/s10494-010-9294-z⟩
resume: This paper reports large eddy simulations of the interaction between an atmospheric boundary layer and a canopy (representing a forest cover). The problem is studied for a homogeneous configuration representing the situation encountered above a continuous forest cover, as well as for a heterogeneous configuration representing the situation similar to an edge or a clearing in a forest. The numerical results reproduces correctly all the main characteristics of this flow as reported in the literature: the formation of a first generation of coherent structures aligned transversally with the wind flow direction, the reorganization and the deformation of these vortex tubes into horse-shoe structures. The results obtained when introducing a discontinuity in the canopy (reproducing a clearing or a fuel break in a forest), are compared with the experimental data collected in a wind tunnel; here, the results confirm the existence of a strong turbulence activity inside the canopy at a distance equal to 8 times the height of the canopy, referenced in the literature as the Enhance Gust Zone (EGZ) characterized by a local peak of the skewness factor.
typdoc: Article dans une revue
DOI: DOI : 10.1007/s10494-010-9294-z
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Proceedings/Recueil des communications

titre: Numerical study of the interaction between a head fire and a backfire propagating in grassland
auteur: Dominique Morvan, Sofiane Meradji, E. Mell William
article: 10th IAFSS Symposium, 2011, France. 10, pp.1415-1424, 2011, Fire Safety Science, ⟨10.3801/IAFSS.FSS.10-1415⟩
resume: One of the objectives of this paper was to simulate numerically the interaction between two line fires ignited in a grassland, on a flat terrain, perpendicularly to the wind direction, in such a way that the two fire fronts (a head fire and a backfire) propagated in opposite directions parallel to the wind. The numerical simulations were conducted in 3D using the new fuel element module recently implemented in WFDS. We chose a grassland for the fuel layer, because it represents certainly one of the most studied ecosystem, in the frame of experimental campaigns to study the behaviour of surface fires at large scale. The aim of this numerical study is to understand what are the physical phenomena and the favorable conditions of ignition of a counter fire, during a fire suppression operation. The preliminary results highlighted that the two fire fronts interacted only at a relative short distance (10-20 m), following this scenario: • The thermal plume above the head fire (representing the main fire front) formed a sort of shelter, protecting the backfire to the direct effect of the wind flow • Before the merging between the two fire fronts, an in-draft flow was observed ahead of the head fire, promoting and accelerating the propagation of the backfire During the last step of the merging of the two fire fronts, a sudden increase of the heat release rate was observed, indicating a significant interaction between the two fires, which can potentially represent a safety problem for people in charge of this kind of operation.
typdoc: Proceedings/Recueil des communications
DOI: DOI : 10.3801/IAFSS.FSS.10-1415
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2010

Article dans une revue

titre: Численное моделирование когерентных структур при распростра-нении примеси в атмосферном пограничном слое над лесным пологом
auteur: Дмитрий Викторович Любимов, Константин Алексеевич Гаврилов, Dominique Morvan, Gilbert Accary, Sofiane Meradji, Олег Аркадьевич Бессонов
article: Вычислительная механика сплошных сред, 2010, 3 (2), pp.34--45
resume: no abstract
typdoc: Article dans une revue
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Chapitre d'ouvrage

titre: Large eddy simulation of coherent structures over forest canopy
auteur: Konstantin Gavrilov, Gilbert Accary, Dominique Morvan, Dimitry Lyubimov, Oleg A Bessonov, Sofiane Meradji
article: Deville M.; Lê T-H.; Sagaut P. Turbulence and Interactions: Proceedings the TI 2009 conference, Springer, pp.143-149, 2010, Notes on Numerical Fluid Mechanics and Multidisciplinary Design, 9783642141386. ⟨10.1007/978-3-642-14139-3_17⟩
resume: This paper deals with the numerical simulation (using a LES approach) of the interaction between an atmospheric boundary layer (ABL) and a canopy, representing a forest cover. This problem was studied for a homogeneous configuration representing the situation encountered above a continuous forest cover, and a heterogeneous configuration representing the situation similar to an edge or a clearing in a forest. The numerical results, reproduced correctly all the main characteristics of this flow, as reported in the literature: the formation of a first generation of coherent structures aligned transversally from the wind flow direction, the reorganisation and the deformation of these vortex tubes to horse shoe structures. The results obtained, introducing a discontinuity in the canopy (reproducing a clearing or a fuel break in a forest), were compared with experimental data collected in a wind tunnel. The results confirmed the existence of a strong turbulence activity inside the canopy at a distance equal to 8 times the height of the canopy, referenced in the literature as an Enhance Gust Zone (EGZ) characterized by a local peak of the skewness factor.
typdoc: Chapitre d'ouvrage
DOI: DOI : 10.1007/978-3-642-14139-3_17
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2009

Article dans une revue

titre: Physical modelling of fire spread in grasslands
auteur: D Morvan, Sofiane Meradji, G Accary
article: Fire Safety Journal, 2009, 44 (1), pp.50--61
resume: no abstract
typdoc: Article dans une revue
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2008

Article dans une revue

titre: Towards a numerical benchmark for 3D mixed-convection low Mach number flows in a rectangular channel heated from below
auteur: Gilbert Accary, Sofiane Meradji, Dominique Fougere, Dominique Morvan
article: Journal of Fluid Dynamics and Material Science, 2008, 141 (1), p. 1-7
typdoc: Article dans une revue
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titre: Coefficients de diffusion des solides dans le dioxyde de carbone supercritique: modélisation du comportement critique
auteur: Isabelle Raspo, Christophe Nicolas, Evelyne Neau, Sofiane Meradji
article: Fluid Phase Equilibria, 2008, 263 (2), pp.214-222. ⟨10.1016/j.fluid.2007.09.025⟩
resume: Most of the models proposed in literature for binary diffusion coefficients of solids in supercritical fluids are restricted to infinite dilution; this can be explained by the fact that most of experimental data are performed in the dilute range. However some industrial processes, such as supercritical fluid separation, operate at finite concentration for complex mixtures. In this case, the concentration dependence of diffusion coefficients must be considered, especially near the upper critical endpoint (UCEP) where a strong decrease of diffusion coefficients was experimentally observed. In order to represent this slowing down, a modified version of the Darken equation was proposed in literature for naphthalene in supercritical carbon dioxide. In this paper, the conditions of application of such a modelling are investigated. In particular, we focus on the order of magnitude of the solubility of the solid and on the vicinity of the critical endpoint. Various equations proposed in literature for the modelling of the infinite dilution diffusion coefficients of the solutes are also compared. Ten binary mixtures of solids with supercritical carbon dioxide were considered for this purpose.
typdoc: Article dans une revue
DOI: DOI : 10.1016/j.fluid.2007.09.025
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titre: Diffusion coefficients of solids in supercritical carbon dioxide: Modelling of near critical behaviour
auteur: Isabelle Raspo, Christophe Nicolas, Evelyne Neau, Sofiane Meradji
article: Fluid Phase Equilibria, 2008, 263, pp.214-222
typdoc: Article dans une revue
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Communication dans un congrès

titre: Three-dimensional numerical simulation of the interaction between natural convection and radiation in a differentially heated cavity in the low Mach number approximation
auteur: Gilles Scarella, Gilbert Accary, Sofiane Meradji, Dominique Morvan, Oleg Bessonov
article: ICHMT International Symposium on Advances in Computational Heat Transfer, May 2008, Marrakech, Morocco
typdoc: Communication dans un congrès
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2007

Article dans une revue

titre: Wildfire behavior study in a Mediterranean pine stand using a physically based model
auteur: D Morvan, Sofiane Meradji, G Accary
article: Combustion Science and Technology, 2007, 180 (2), pp.230--248
resume: no abstract
typdoc: Article dans une revue
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titre: Réaction hétérogène déclenchée par l'effet piston dans des mélanges binaires supercritiques
auteur: Isabelle Raspo, Sofiane Meradji, Bernard Zappoli
article: Chemical Engineering Science, 2007, 62 (16), pp.4182-4192. ⟨10.1016/j.ces.2007.04.027⟩
resume: It is now well established that the large compressibility of supercritical fluids is responsible for the strong enhancement of the thermo-acoustic heating, leading to the speeding up of the heat transport thanks to the piston effect instead of the expected slowing down. We show in this paper, through numerical simulations, that the hydrodynamics behavior of supercritical fluids also couples with the critical behavior of the solubility of solids to cause the release of a heterogeneous reaction at solid surfaces in dilute binary supercritical mixtures.
typdoc: Article dans une revue
DOI: DOI : 10.1016/j.ces.2007.04.027
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2005

Article dans une revue

titre: The Sanchez-Lacombe lattice fluid model for the modeling of solids in supercritical fluids
auteur: Christophe Nicolas, Evelyne Neau, Sofiane Meradji, Isabelle Raspo
article: Fluid Phase Equilibria, 2005, 232 (1-2), pp.219-229. ⟨10.1016/j.fluid.2005.03.015⟩
resume: The Sanchez-Lacombe equation of state is known to describe the thermodynamic properties of molecular fluids of arbitrary size, especially polymer-solvent phase behavior. However, it is rarely used for modeling solid-supercritical fluid equilibria. In this work, it is shown that a proper estimation of the EoS characteristic parameters together with a thermodynamically consistent expression of fugacity coefficients allows a satisfactory correlation of the solubility of solids in the supercritical phase. Binary mixtures containing carbon dioxide, ethane, ethylene and xenon were considered for this purpose. In a first step, the consistency of experimental data was checked using variance analysis. Then, different mixing rules were considered and results compared with those obtained with the Peng-Robinson equation. Finally, the lower and upper boundaries of the solid-liquid-vapor regions (LCEP and UCEP) were also determined and compared with experimental values.
typdoc: Article dans une revue
DOI: DOI : 10.1016/j.fluid.2005.03.015
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2001

Article dans une revue

titre: 2D unsteady motion and deformation of a gaseous bubble in a vibrating liquid at zero gravity
auteur: Dv Lyubimov, Tp Lyubimova, Sofiane Meradji, Bernard Roux, D Beysens, Y Garrabos, D Chatain
article: Journal de Physique IV Proceedings, 2001, 11 (PR6), pp.Pr6--91
resume: no abstract
typdoc: Article dans une revue
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titre: Numerical simulation of a liquid drop freely oscillating
auteur: Sofiane Meradji, Tp Lyubimova, Dv Lyubimov, B Roux
article: Crystal Research and Technology, 2001, 36 (7), pp.729--744
resume: no abstract
typdoc: Article dans une revue
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1997

Article dans une revue

titre: Vibrational control of crystal growth from liquid phase
auteur: Dv Lyubimov, Tp Lyubimova, Sofiane Meradji, B Roux
article: Journal of Crystal Growth, 1997, 180 (3), pp.648--659
resume: no abstract
typdoc: Article dans une revue
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