L'ignition de la matière végétale (thèse: 2012 - 2015)
-en- Activités
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-en- Publications scientifiques au M2P2
2018
Mohamad El Houssami, Aymeric Lamorlette, Dominique Morvan, Rory M Hadden, Albert Simeoni. Framework for submodel improvement in wildfire modeling. Combustion and Flame, 2018, 190, pp.12-24. ⟨10.1016/j.combustflame.2017.09.038⟩. ⟨hal-02114000⟩ Plus de détails...
An experimental and numerical study was carried out to assess the performance of the different sub-models and parameters used to describe the burning dynamics of wildfires. A multiphase formulation was used and compared to static fires of dried pitch pine needles of different bulk densities. The samples were exposed to an external heat flux of 50 kW/m 2 in the FM Global Fire Propagation Apparatus and subjected to different airflows, providing a controlled environment and repeatable conditions. Sub-models for convective heat transfer, drag forces, and char combustion were investigated to provide mass loss rate, flaming duration, and gas emissions. Good agreement of predicted mass loss rates and heat release rates was achieved, where all these submodels were selected to suit the tested conditions. Simulated flaming times for different flow conditions and different fuel bulk densities compared favorably against experimental measurements. The calculation of the drag forces and the heat transfer coefficient was demonstrated to influence greatly the heating/cooling rate, the degradation rate, and the flaming time. The simulated CO and CO 2 values compared well with experimental data, especially for reproducing the transition between flaming and smoldering. This study complements a previous study made with no flow to propose a systematic approach that can be used to assess the performance of the submodels and to better understand how specific physical phenomena contribute to the wildfire dynamics. Furthermore, this study underlined the importance of selecting relevant submodels and the necessity of introducing relevant subgrid-scale modelling for larger scale simulations.
Mohamad El Houssami, Aymeric Lamorlette, Dominique Morvan, Rory M Hadden, Albert Simeoni. Framework for submodel improvement in wildfire modeling. Combustion and Flame, 2018, 190, pp.12-24. ⟨10.1016/j.combustflame.2017.09.038⟩. ⟨hal-02114000⟩
Aymeric Lamorlette, Mohamad El Houssami, Dominique Morvan. An improved non-equilibrium model for the ignition of living fuel. International Journal of Wildland Fire, 2018, 27 (1), pp.29-41. ⟨10.1071/Wf17020⟩. ⟨hal-02114417⟩ Plus de détails...
This paper deals with the modelling of living fuel ignition, suggesting that an accurate description using a multiphase formulation requires consideration of a thermal disequilibrium within the vegetation particle, between the solid (wood) and the liquid (sap). A simple model at particle scale is studied to evaluate the flux distribution between phases in order to split the net flux on the particles into the two sub-phases. An analytical solution for the split function is obtained from this model and is implemented in ForestFireFOAM, a computational fluid dynamics (CFD) solver dedicated to vegetation fire simulations, based on FireFOAM. Using this multiphase formulation, simulations are run and compared with existing data on living fuel flammability. The following aspects were considered: fuel surface temperature, ignition, flaming combustion time, mean and peak heat release rate (HRR). Acceptable results were obtained, suggesting that the thermal equilibrium might not be an acceptable assumption to properly model ignition of living fuel.
Aymeric Lamorlette, Mohamad El Houssami, Dominique Morvan. An improved non-equilibrium model for the ignition of living fuel. International Journal of Wildland Fire, 2018, 27 (1), pp.29-41. ⟨10.1071/Wf17020⟩. ⟨hal-02114417⟩
Mohamad El Houssami, J.C. Thomas, Aymeric Lamorlette, Dominique Morvan, M. Chaos, et al.. Experimental and numerical studies characterizing the burning dynamics of wildland fuels. Combustion and Flame, 2016, 168, pp.113-126. ⟨10.1016/j.combustflame.2016.04.004⟩. ⟨hal-01345741⟩ Plus de détails...
A method to accurately understand the processes controlling the burning behavior of porous wildland fuels is presented using numerical simulations and laboratory experiments. A multiphase approach has been implemented in OpenFOAM, which is based on the FireFOAM solver for large eddy simulations (LES). Conservation equations are averaged in a control volume containing a gas and a solid phase. Drying, pyrolysis, and char oxidation are described by interaction between the two phases. Numerical simulations are compared to laboratory experiments carried out with porous pine needle beds in the FM Global Fire Propagation Apparatus (FPA). These experiments are used to support the use and the development of submodels that represent heat transfer, pyrolysis, gas-phase combustion, and smoldering processes. The model is tested for different bulk densities, two distinct species and two different radiative heat fluxes used to heat up the samples. It has been possible to reproduce mass loss rates, heat release rates, and temperatures that agree with experimental observations, and to highlight the current limitations of the model.
Mohamad El Houssami, J.C. Thomas, Aymeric Lamorlette, Dominique Morvan, M. Chaos, et al.. Experimental and numerical studies characterizing the burning dynamics of wildland fuels. Combustion and Flame, 2016, 168, pp.113-126. ⟨10.1016/j.combustflame.2016.04.004⟩. ⟨hal-01345741⟩
Aymeric Lamorlette, Mohamad El Houssami, Jan C. Thomas, Albert Simeoni, Dominique Morvan. A dimensional analysis of forest fuel layer ignition model: Application to the ignition of pine needle litters. Journal of Fire Sciences, 2015, pp.NC. ⟨10.1177/ToBeAssigned⟩. ⟨hal-01157866⟩ Plus de détails...
This paper deals with the physical modelling of forest fuel layer ignition. A model based on momentum, fluid and solid phase energy equations is written for a fuel layer and a dimensional analysis is performed. This analysis allows to enlighten two relevant dimensionless groups regarding the dimensionless time to ignition of a fuel layer and also provides a suited scaling for the fluid velocity inside the fuel layer during ignition. A correlation for the time to ignition is then fitted on experimental data obtained using a FM-Global Fire Propagation Apparatus (FPA) for different pine species with a closed basket. A good agreement is found, emphasizing the relevance of the dimensionless groups and the thermally thick behaviour of the solid particles during the ignition process under incident radiant heat flux as low as 8 − 12kW.m −2 .
Aymeric Lamorlette, Mohamad El Houssami, Jan C. Thomas, Albert Simeoni, Dominique Morvan. A dimensional analysis of forest fuel layer ignition model: Application to the ignition of pine needle litters. Journal of Fire Sciences, 2015, pp.NC. ⟨10.1177/ToBeAssigned⟩. ⟨hal-01157866⟩
