Modeling and simulation of forest fire propagation
Mixture thermodynamics
Thermodynamics, Numerical Waves, Interfaces, Combustion Team
Présentation
The TONIC team is developing an activity of modeling of strongly multi-scale phenomena. It covers in particular multiphase and/or reactive flows, from the scale of the isolated injector (a few mm) to the scale of a fully developed forest fire (several hectares).
Adapted numerical methods are developed in parallel, in particular for soil imaging (detection of slicks by acoustic analysis), or for the modeling of radiative transfers.
In parallel to these multi-scale developments, analytical work is carried out to support the construction of models. An important research effort is devoted to the modeling of the thermodynamics of multiphase mixtures (thermochemical equilibrium calculations, complex thermodynamic closures), or to the development of reduced kinetic models for combustion.
équipe Thermodynamiques, Ondes, Numérique, Interfaces et Combustion
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Dernières publications de l'équipe
2021
Oleksandr Dimitrov, Pierrette Guichardon, Isabelle Raspo, Evelyne Neau. Vapor–Liquid Equilibria of the Aqueous and Organic Mixtures Composed of Dipropylene Glycol Methyl Ether, Dipropylene Glycol n -Butyl Ether, and Propylene Glycol n -Butyl Ether. Part II: Modeling Based on the NRTL-PR Model. Industrial and engineering chemistry research, American Chemical Society, 2021, 60 (30), pp.11513-11524. ⟨10.1021/acs.iecr.1c01545⟩. ⟨hal-03379757⟩ Plus de détails...
Further to the Part I of the present paper, the second Part is concentrated around the VLE modeling of binary mixtures involving the three glycol ethers previously studied experimentally. The authors propose to use the NRTL-PR model for the representation of these non-ideal mixtures. The main difficulties of modelling related to very low vapor pressures and the way of dealing with them are highlighted. The unknown critical parameters for DPM, DPnB and PnB were determined using robust group contribution methods. However, the experimental values of these parameters have never been published before. The main goal of the authors was to obtain the most satisfactory representation of the experimental data provided in the Part I. Some issues that mostly occurred in mixtures involving the PnB as well as in mixtures having very low vapor pressures, were encountered. Nevertheless, we have obtained in general a satisfactory representation of measured points regardless of those issues.
Oleksandr Dimitrov, Pierrette Guichardon, Isabelle Raspo, Evelyne Neau. Vapor–Liquid Equilibria of the Aqueous and Organic Mixtures Composed of Dipropylene Glycol Methyl Ether, Dipropylene Glycol n -Butyl Ether, and Propylene Glycol n -Butyl Ether. Part II: Modeling Based on the NRTL-PR Model. Industrial and engineering chemistry research, American Chemical Society, 2021, 60 (30), pp.11513-11524. ⟨10.1021/acs.iecr.1c01545⟩. ⟨hal-03379757⟩
Journal: Industrial and engineering chemistry research
Pierre Boivin, M. Tayyab, S. Zhao. Benchmarking a lattice-Boltzmann solver for reactive flows: Is the method worth the effort for combustion?. Physics of Fluids, American Institute of Physics, 2021, 33 (7), pp.071703. ⟨10.1063/5.0057352⟩. ⟨hal-03276189⟩ Plus de détails...
Pierre Boivin, M. Tayyab, S. Zhao. Benchmarking a lattice-Boltzmann solver for reactive flows: Is the method worth the effort for combustion?. Physics of Fluids, American Institute of Physics, 2021, 33 (7), pp.071703. ⟨10.1063/5.0057352⟩. ⟨hal-03276189⟩
Nicolas Frangieh, Gilbert Accary, Jean-Louis Rossi, Dominique Morvan, Sofiane Meradji, et al.. Fuelbreak effectiveness against wind-driven and plume-dominated fires: a 3D numerical study. Fire Safety Journal, Elsevier, 2021, pp.103383. ⟨10.1016/j.firesaf.2021.103383⟩. ⟨hal-03258935⟩ Plus de détails...
The effectiveness of a fuelbreak, created in a homogeneous grassland on a flat terrain, was studied numerically. The analysis relies on 3D numerical simulations that were performed using a detailed physical-fire-model (FIRESTAR3D) based on a multiphase formulation. To avoid border effects, calculations were carried out by imposing periodic boundary conditions along the two lateral sides of the computational domain, reproducing that way a quasi-infinitely long fire front. A total of 72 simulations were carried out for various wind speeds, fuel heights, and fuelbreak widths, which allowed to cover a large spectrum of fire behaviour, ranging from plume-dominated fires to wind-driven fires. The results were classified in three main categories: 1- “Propagation” if fire crossed the fuelbreak with a continuous fire front, 2- “Overshooting” and “Marginal” if fire marginally crosses the fuelbreak with the formation of burning pockets, and 3- “No propagation” if fire does not cross at all the fuelbreak. The ratio of fuelbreak width to fuel height, marking the “Propagation”/“No propagation” transition, was found to be scaled with Byram's convection number Nc as 75.07 × Nc−0.46. The numerical results were also compared to an operational wildfire engineering tool (DIMZAL) dedicated to fuelbreaks dimensioning.
Nicolas Frangieh, Gilbert Accary, Jean-Louis Rossi, Dominique Morvan, Sofiane Meradji, et al.. Fuelbreak effectiveness against wind-driven and plume-dominated fires: a 3D numerical study. Fire Safety Journal, Elsevier, 2021, pp.103383. ⟨10.1016/j.firesaf.2021.103383⟩. ⟨hal-03258935⟩
M. Tayyab, S. Zhao, Pierre Boivin. Lattice-Boltzmann modeling of a turbulent bluff-body stabilized flame. Physics of Fluids, American Institute of Physics, 2021, 33 (3), pp.031701. ⟨10.1063/5.0038089⟩. ⟨hal-03160901⟩ Plus de détails...
This letter reports the first large eddy simulation of a turbulent flame using a Lattice-Boltzmann model. To that end, simulation of a bluff-body stabilized propane-air flame is carried out, showing an agreement similar to those available in the literature. Computational costs are also reported, indicating that Lattice-Boltzmann modelling of reactive flows is competitive, with around 1000cpuh required to simulate one residence time in the 1,5m burner.
M. Tayyab, S. Zhao, Pierre Boivin. Lattice-Boltzmann modeling of a turbulent bluff-body stabilized flame. Physics of Fluids, American Institute of Physics, 2021, 33 (3), pp.031701. ⟨10.1063/5.0038089⟩. ⟨hal-03160901⟩
G. Farag, S. Zhao, G. Chiavassa, Pierre Boivin. Consistency study of Lattice-Boltzmann schemes macroscopic limit. Physics of Fluids, American Institute of Physics, 2021, 33 (3), pp.037101. ⟨10.1063/5.0039490⟩. ⟨hal-03160898⟩ Plus de détails...
Owing to the lack of consensus about the way Chapman-Enskog should be performed, a new Taylor-Expansion of Lattice-Boltzmann models is proposed. Contrarily to the Chapman-Enskog expansion, recalled in this manuscript, the method only assumes an su ciently small time step. Based on the Taylor expansion, the collision kernel is reinterpreted as a closure for the stress-tensor equation. Numerical coupling of Lattice-Boltzmann models with other numerical schemes, also encompassed by the method, are shown to create error terms whose scalings are more complex than those obtained via Chapman-Enskog. An athermal model and two compressible models are carefully analyzed through this new scope, casting a new light on each model's consistency with the Navier-Stokes equations.
G. Farag, S. Zhao, G. Chiavassa, Pierre Boivin. Consistency study of Lattice-Boltzmann schemes macroscopic limit. Physics of Fluids, American Institute of Physics, 2021, 33 (3), pp.037101. ⟨10.1063/5.0039490⟩. ⟨hal-03160898⟩
Février 2022
- Lattice-Boltzmann methods for compressible flows / PhD defense Gabriel Farag
Doctorant : Fabriel FARAG
Date de soutenance : le 4 février 2022 à 14h00 ; Amphi 3 Centrale Marseille
Abstract : Since the late 1970's, computational fluid dynamics solvers became essentials due to increasingly complex applications requiring fluid solutions. The small scales necessary for industrial applications often need a very fine grid or very small timestep. This dramatically increases the computational cost of nowadays simulations. To design more computationally efficient solvers, a popular approach is to use Lattice-Boltzmann methods. Originating from the kinetic theory of gases, this method have gained a tremendous popularity among fluid dynamicists due to its cheap and easily implemented collide & stream algorithm. However, its intrinsic assumptions confines classical Lattice-Boltzmann solvers to weakly compressible flows. Yet, some compressible models have been proposed. The purpose of this manuscript is to improve the robustness as well as accuracy of compressible Lattice-Boltzmann models. To this end, the Lattice-Boltzmann method is fully reinterpreted as a numerical scheme. This allows a straightforward and parsimonious derivation of the equivalent Navier-Stokes-Fourier system using the sole assumption of a negligible timestep. Using this formalism, the order of accuracy is shown to depend on the collision kernel, as well as the mechanical constitutive model. Various models are investigated and we show that the Knudsen number is not the sole parameter controlling the consistency with the Navier-Stokes-Fourier model. Additionally, capabilities of the entropy equation to model low supersonic flows is explained through standard shock wave theory arguments. A MUSCL-Hancock scheme is employed to discretize the entropy equation and improve both stability and accuracy compared to previous schemes. Equipped with this new formalism, a compressible pressure-based model is proposed and validated on various supersonic test cases. Then, we unify all compressible models proposed by our group under a single formalism and investigate the differences and optimal choices for the various degrees of freedom of our family of models. Finally, this unified model is validated on high supersonic smooth flows and low supersonic shocked flows.
Jury
Directeur de these M. Pierre BOIVIN CNRS / M2P2
CoDirecteur de these M. Guillaume CHIAVASSA Centrale Marseille
Examinateur M. Manfred KRAFCZYK Technische Universität Braunschweig
Examinateur M. Pierre SAGAUT Aix-Marseille Université / M2P2
Vendredi 18 décembre
- Instabilités strato-rotationelles : calcul intensif et expérience / Soutenance de thèse Gabriel MELETTI DE OLIVEIRA
Doctorant : Gabriel MELETTI DE OLIVEIRA
Date de la soutenance : le 18 décembre 2020 à 10h00, au bâtiment AZFD de la Brandenburg University of Technology Cottbus – Senftenberg
Abstract :
Les vortex en écoulements stratifiés peuvent se manifester à petite et grande échelles dans les applications géophysique et astrophysique. Dans le contexte astrophysique, les disques d’accrétion (à partir desquels les systèmes solaires sont formés) peuvent être considérés comme des tourbillons en milieux stratifiés. En ce qui concerne la formation des planètes, la compréhension des mécanismes qui peuvent entraîner un transport vers l’extérieur du moment cinétique constitue par conséquent un problème central. Pour qu’une planète ou une étoile se forme dans un disque, le moment angulaire doit être transporté loin de son centre afin de permettre l’agrégation de matière par gravité; sinon, sa vitesse de rotation serait beaucoup trop grande pour permettre cette agrégation de matière (et la formation d’étoiles qui en résulte). Dans de tels systèmes constitués de gaz, la turbulence est le mécanisme le plus probable permettant de réaliser un transport de moment angulaire aussi important. Cependant, il a été montré que le profil des écoulements des disques d’accrétion est stable et la question se pose de savoir com-ment la turbulence peut être générée. Parmi les autres candidats, l’instabilité strato-rotationnelle (SRI) a attiré l’attention ces dernières années. SRI est une instabilité purement hydrodynamique qui peut être modélisée par un système classique de Taylor-Couette (TC) avec une stratification stable due à un gradient axial de salinité ou de température. Dans cette thèse, on proposes une étude à la fois expérimentale et numérique en se focalisant sur la mise en évidence de nouveaux comportements spécifiques à l’instabilité strato-rotationnelle (SRI). La stratification axiale provoque un changement de la transition de l’instabilité marginale par rapport au système classique non stratifié TC, rendant l’écoulement instable dans les régions où sans stratification il resterait stable. Cette caractéristique fait de l’instabilité SRI un phénomène pertinent dans les domaines planétaire et astrophysique, en particulier dans la théorie de la formation des disques d’accrétion. Malgré de nombreuses avancées dans la compréhension des écoulements strato-rotationnels,la confrontation de données expérimentales avec des simulations numériques non linéaires est pertinente, car elle implique à la fois les aspects linéaires ainsi que les interactions non linéaires des modes SRI qui doivent encore être mieux compris. Ces comparaisons révèlent également de nouveaux phénomènes et motifs non linéaires encore jamais observés pour les SRI, contribuant ainsi à une meilleure compréhension des écoulements géophysiques. Le dispositif expérimental conçu pour étudier ces phénomènes liés à l’instabilité SRI consiste en deux cylindres qui peuvent tourner indépendamment, la cavité étant remplie avec de l’huile de silicone. Afin d’obtenir une stratification stable le long de l’axe du cylindre, le couvercle inférieur de l’installation est refroidi tandis que sa partie supérieure est chauffée. Le champ résultant de la rotation des cylindres interagissant avec la stratification de densité stable est mesuré en utilisant la technique de vélocimétrie par image de particules (PIV). Dans cette thèse, nous nous sommes concentrés sur des cas à nombres de Reynolds modérés (Re, basé sur le rayon du cylindre intérieur et les vitesses angulaires), variant entre Re=300 et Re=1300. Le rapport de rotation entre cylindres extérieur et intérieur est fixé à μ=Ωout/Ωin=0.35, une valeur légèrement inférieure au profil de vitesse képlérien, mais au delà de la limite de Rayleigh. Cette configuration expérimentale est également étudiée par simulations numériques directes à l’aide d’un code parallèle incompressible avec une approximation de Boussinesq, basé sur des schémas compacts d’ordre élevé et des séries de Fourier.D’un point de vue algorithmique, une décomposition bi-dimensionnelle est mise en œuvre afin d'obtenir une parallélisation efficace.
Jury :
Directeur de thèse: Stéphane Viazzo (Aix-Marseille Université, M2P2)
Directeur de thèse: Uwe Harlander (BTU Cottbus-Seftenberg)
Rapporteur: Innocent Mutabazi (Université du Havre)
Rapporteur: Christoph Egbers ( BTU Cottbus-Seftenberg)
Examinatrice: Caroline Nore (Université Paris Saclay)
