de la matière brute homogène inerte à la matière hétérogène,
réactive et présentant éventuellement des déséquilibres entre phases
Publications scientifiques au M2P2
2020
Kai Zhang, Aymeric Lamorlette. An extensive numerical study of the burning dynamics of wildland fuel using proposed configuration space. International Journal of Heat and Mass Transfer, 2020, 160, pp.120174. ⟨10.1016/j.ijheatmasstransfer.2020.120174⟩. ⟨hal-02960139⟩ Plus de détails...
Physics-based flame models capable of predicting small-scale fire behaviors reduce computational power needed for predicting fires of large- and giga-scale. However, classical model correlations are often developed for 'free fires' without considering vegetation around. These models may result in inaccurate fire modeling due to wrong 'prior' flame shape estimated from theta similar to wind speed. To overcome this defect, three-dimensional small-scale fires with fireline intensity of 100 KW/m are numerically simulated using large eddy simulation. Fire behaviors such as flame tilt angle and heat transfer mechanisms are extensively studied using a newly proposed configuration space {N-C, CdLAI}. The former one represents the ratio between fire to wind power, and the latter one considering the vegetation effect is for the first time introduced in flame models. Using the configuration space, two model correlations for flame tilt angle and radiative heat power reaching the unburnt fuels are proposed. The flame tilt angle theta is directly related to CdLAI (C-d alpha(s)sigma H-s(F)/2), while inversely related to N-C (2gI/ rho 0C(p,0)T(0)U(0)(3)), in contrast to the model proposed for radiative heat power. Comparisons with several classical models evidenced the capability of new flame models in predicting both free and non-free fires. The limits of the validity of the newly proposed models are also discussed.
Kai Zhang, Aymeric Lamorlette. An extensive numerical study of the burning dynamics of wildland fuel using proposed configuration space. International Journal of Heat and Mass Transfer, 2020, 160, pp.120174. ⟨10.1016/j.ijheatmasstransfer.2020.120174⟩. ⟨hal-02960139⟩
Journal: International Journal of Heat and Mass Transfer
Kai Zhang, Salman Verma, Arnaud Trouvé, Aymeric Lamorlette. A study of the canopy effect on fire regime transition using an objectively defined Byram convective number. Fire Safety Journal, 2020, 112, pp.102950. ⟨10.1016/j.firesaf.2020.102950⟩. ⟨hal-02469260⟩ Plus de détails...
Kai Zhang, Salman Verma, Arnaud Trouvé, Aymeric Lamorlette. A study of the canopy effect on fire regime transition using an objectively defined Byram convective number. Fire Safety Journal, 2020, 112, pp.102950. ⟨10.1016/j.firesaf.2020.102950⟩. ⟨hal-02469260⟩
Kai Zhang, Salman Verma, Arnaud Trouvé, Aymeric Lamorlette. A study of the canopy effect on fire regime transition using an objectively defined Byram convective number. Fire Safety Journal, Elsevier, 2020, 112, pp.102950. ⟨10.1016/j.firesaf.2020.102950⟩. ⟨hal-02469260⟩ Plus de détails...
Kai Zhang, Salman Verma, Arnaud Trouvé, Aymeric Lamorlette. A study of the canopy effect on fire regime transition using an objectively defined Byram convective number. Fire Safety Journal, Elsevier, 2020, 112, pp.102950. ⟨10.1016/j.firesaf.2020.102950⟩. ⟨hal-02469260⟩
Kai Zhang, Aymeric Lamorlette. An extensive numerical study of the burning dynamics of wildland fuel using proposed configuration space. International Journal of Heat and Mass Transfer, 2020, 160, pp.120174. ⟨10.1016/j.ijheatmasstransfer.2020.120174⟩. ⟨hal-03232086⟩ Plus de détails...
Physics-based flame models capable of predicting small-scale fire behaviors reduce computational power needed for predicting fires of large- and giga-scale. However, classical model correlations are often developed for 'free fires' without considering vegetation around. These models may result in inaccurate fire modeling due to wrong 'prior' flame shape estimated from theta similar to wind speed. To overcome this defect, three-dimensional small-scale fires with fireline intensity of 100 KW/m are numerically simulated using large eddy simulation. Fire behaviors such as flame tilt angle and heat transfer mechanisms are extensively studied using a newly proposed configuration space {N-C, CdLAI}. The former one represents the ratio between fire to wind power, and the latter one considering the vegetation effect is for the first time introduced in flame models. Using the configuration space, two model correlations for flame tilt angle and radiative heat power reaching the unburnt fuels are proposed. The flame tilt angle theta is directly related to CdLAI (C-d alpha(s)sigma H-s(F)/2), while inversely related to N-C (2gI/ rho 0C(p,0)T(0)U(0)(3)), in contrast to the model proposed for radiative heat power. Comparisons with several classical models evidenced the capability of new flame models in predicting both free and non-free fires. The limits of the validity of the newly proposed models are also discussed.
Kai Zhang, Aymeric Lamorlette. An extensive numerical study of the burning dynamics of wildland fuel using proposed configuration space. International Journal of Heat and Mass Transfer, 2020, 160, pp.120174. ⟨10.1016/j.ijheatmasstransfer.2020.120174⟩. ⟨hal-03232086⟩
Journal: International Journal of Heat and Mass Transfer
L. Terrei, A. Lamorlette, A. Ganteaume. Modelling the fire propagation from the fuel bed to the lower canopy of ornamental species used in wildland–urban interfaces. International Journal of Wildland Fire, 2019, 28 (2), pp.113. ⟨10.1071/WF18090⟩. ⟨hal-02176483⟩ Plus de détails...
South-eastern France is strongly affected by wildfires mostly occurring in the wildland-urban interfaces (WUIs). A WUI fire is often initiated in dead surface fuel, then can propagate to shrubs and trees when the lower canopy is close to (or touches) the ground. Whereas a previous study assessed the fire propagation from the fuel bed to the lower canopy of different species used as ornamental vegetation in this region, the objectives of the current work consisted of checking if the modelling of this fire propagation was possible using WFDS (Wildland-Urban Interface Fire Dynamical Simulator) in comparing experimental and modelling results. Experimental and modelling constraints (i. e. branch geometric definition, branch motion due to convection) showed differences in some of the recorded data (such as time to ignition, ignition temperature, mass loss and maximum temperature), but comparisons of variation in mass loss and temperature over time showed that modelling the fire propagation at the scale of a branch was possible if the branch fuel-moisture content remained lower than 25%. For both experiments and modelling, the ranking of species according to their branch flammability highlighted identical groups of species.
L. Terrei, A. Lamorlette, A. Ganteaume. Modelling the fire propagation from the fuel bed to the lower canopy of ornamental species used in wildland–urban interfaces. International Journal of Wildland Fire, 2019, 28 (2), pp.113. ⟨10.1071/WF18090⟩. ⟨hal-02176483⟩
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⟩
Rachel Aganetti, Aymeric Lamorlette, G.R. Thorpe. The relationship between external and internal flow in a porous body using the penalisation method. International Journal of Heat and Fluid Flow, 2017, 66 (66), pp.185 - 196. ⟨10.1016/j.ijheatfluidflow.2017.06.003⟩. ⟨hal-01547073⟩ Plus de détails...
Stockpiles of organic porous materials such as biosolids, coal, compost and woodchips are susceptible to spontaneous combustion. Flow fields within such materials are induced by buoyant forces and external agents such as the wind. However, the external forces may vary on a time scale of seconds, whereas the heat, mass and momentum processes within the porous medium may occur over timescales days or months. It would be computationally prohibitive to resolve all of the timescales, hence in this paper mean external forces are coupled to the flow field within stockpiles of biosolids by means of a penalisation method. It has been determined that four variables have a profound influence of the flow fields within porous media. These are the velocity of the wind, the permeability of the porous biosolids, the angle of repose of the medium and aspect ratio of the stockpile. Four distinct flow regimes within the stockpiles have been identified. A correlation has been developed to assist managers of stockpiles, which relates mean velocities within the four flow regimes with a Darcy and Reynolds number, the aspect ratio and angle of repose. The correlation is accurate for two of the four flow regions identified, but the error in predicting the two remaining regions is relatively large. However, this error is expected to have minimal impact on estimating the time for spontaneous combustion to occur.
Rachel Aganetti, Aymeric Lamorlette, G.R. Thorpe. The relationship between external and internal flow in a porous body using the penalisation method. International Journal of Heat and Fluid Flow, 2017, 66 (66), pp.185 - 196. ⟨10.1016/j.ijheatfluidflow.2017.06.003⟩. ⟨hal-01547073⟩
Journal: International Journal of Heat and Fluid Flow
Rachael Aganetti, Aymeric Lamorlette, Guilbert Emilie, Dominique Morvan, G.R. Thorpe. Advection and the self-heating of organic porous media. International Journal of Heat and Mass Transfer, 2016, ⟨10.1016/j.ijheatmasstransfer.2015.11.023⟩. ⟨hal-01345737⟩ Plus de détails...
Self-heating is commonly observed when organic materials such as biosolids, coal, food grains and compost are stockpiled. A convection–diffusion model is presented that accounts for the roles of advection and the transport of oxygen in the self-heating process, as well as the development of an empirical correlation between dimensionless Darcy number, Frank–Kamenetskii parameter and pile aspect ratio, to predict the critical permeability above which thermal runaway can be avoided. It is apparent that the permeability of the stockpile determines the likelihood of the thermal runaway. However, the solids that form a stockpile are poly-disperse and it is essential to determine an effective permeability. This has been achieved using experimental data on biosolids obtained from a wastewater treatment plant in Australia. With this method the model is used to demonstrate how the permeability of a stockpile might be adjusted to reduce the incidence of thermal runaway.
Rachael Aganetti, Aymeric Lamorlette, Guilbert Emilie, Dominique Morvan, G.R. Thorpe. Advection and the self-heating of organic porous media. International Journal of Heat and Mass Transfer, 2016, ⟨10.1016/j.ijheatmasstransfer.2015.11.023⟩. ⟨hal-01345737⟩
Journal: International Journal of Heat and Mass Transfer
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, Fabien Candelier. Thermal behavior of solid particles at ignition: Theoretical limit between thermally thick and thin solids. International Journal of Heat and Mass Transfer, 2015, pp.117-122. ⟨10.1016/j.ijheatmasstransfer.2014.11.037⟩. ⟨hal-01096409⟩ Plus de détails...
This paper deals with thermal behaviors of solid particles at ignition in attempting to theoretically delineate transition between thermally thick and thin behavior when a solid target is exposed to a radiant heat flux. In order to evaluate classical asymptotic relation accuracy and limiting range, models are developed for finite-depth target in both Cartesian and cylindrical coordinates, allowing to enhance asymptotic relations. Comparison between finite-depth target solutions and asymptotic solutions finally provides a mapping which allows the suited relation for ignition time calculation to be determined, regarding ignition conditions. This mapping then suggests some interesting consequences on forest fuel ignition and fire propagation modeling, since asymptotic models seem to overlap on large regions.
Aymeric Lamorlette, Fabien Candelier. Thermal behavior of solid particles at ignition: Theoretical limit between thermally thick and thin solids. International Journal of Heat and Mass Transfer, 2015, pp.117-122. ⟨10.1016/j.ijheatmasstransfer.2014.11.037⟩. ⟨hal-01096409⟩
Journal: International Journal of Heat and Mass Transfer
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⟩
Aymeric Lamorlette. Quantification of ignition time uncertainty based on the classical ignition theory and Fourier analysis. Comptes Rendus Mécanique, 2014, 342 (8), pp.459 - 465. ⟨10.1016/j.crme.2014.06.002⟩. ⟨hal-01096403⟩ Plus de détails...
This study aims at modeling the effect of incoming heat flux fluctuations, on solid material ignition. In order to propose a general methodology based on the classical ignition theory that can be applied to any kind of solid target, kernels accounting for the target temperature response regarding an incoming heat flux are considered for thermally thick and thin solids with low or high thermal inertia. A Fourier decomposition of the incoming heat flux is then used to calculate the target response to harmonic heat fluxes. Finally, effects of harmonic fluctuations on ignition are discussed based on the previous analytical results, allowing to discriminate situations where ignition time is expected to be rather predictable from situations where ignition time is expected to be less predictable thanks to an uncertainty quantification of the ignition time. To cite this article: Aymeric Lamorlette, C. R. Mecanique 333 (2005).
Aymeric Lamorlette. Quantification of ignition time uncertainty based on the classical ignition theory and Fourier analysis. Comptes Rendus Mécanique, 2014, 342 (8), pp.459 - 465. ⟨10.1016/j.crme.2014.06.002⟩. ⟨hal-01096403⟩
Aymeric Lamorlette. Analytical modeling of solid material ignition under a radiant heat flux coming from a spreading fire front. Journal of Thermal Science and Engineering Applications, 2014, 6 (4), pp.044501. ⟨10.1115/1.4028204⟩. ⟨hal-01059491⟩ Plus de détails...
This study aims at characterizing ignition of solid targets exposed to spreading fire fronts. In order to model radiant heat fluxes on targets in a realistic way, polynomial heat fluxes are chosen. Analytical solutions for the solid surface temperature evolution regarding different time-varying heat fluxes are discussed for high thermal inertia solids using a mathematical formalism, which allows for the methodology to be extended to the case of low thermal inertia. This formulation also allows calculation of ignition times for more realistic time-dependent fluxes than previous studies on the topic, providing a more general solution to the problem of solid material ignition. Polynomial coefficients are then obtained fitting heat flux coming from absorbing-emitting flames. A characterization of solid material ignition times regarding fire front rate of spread (ROS) is finally performed, showing the need to accurately model heat flux variations in ignition time calculations.
Aymeric Lamorlette. Analytical modeling of solid material ignition under a radiant heat flux coming from a spreading fire front. Journal of Thermal Science and Engineering Applications, 2014, 6 (4), pp.044501. ⟨10.1115/1.4028204⟩. ⟨hal-01059491⟩
Journal: Journal of Thermal Science and Engineering Applications
Aymeric Lamorlette, Anthony Collin. Analytical quantification of convective heat transfer inside vegetal structures. International Journal of Thermal Sciences, 2012, 57, pp.78-84. ⟨10.1016/j.ijthermalsci.2012.02.010⟩. ⟨hal-01297730⟩ Plus de détails...
Within the scope of environmental modelling, convective heat transfer between a vegetal structure and its surrounding medium remains to be adequately described. However, for some applications, such as forest fire modelling, convective heat transfer is one of the factors responsible for vertical fire transitions, from ground level to the tree crowns. These fires are the most dangerous because their rates of spread can reach high speeds, around 1 m per second. An accurate characterization of this transfer is therefore important for fire propagation modelling. This study presents an attempt to formulate an analytical modelling of the convective heat transfer coefficient inside vegetal structures generated using an Iterated Function Systems (IFS) which only depends on the IFS parameters (parameters helpful to generate vegetal structures). The results obtained using this formula are compared with previously computed numerical results to evaluate their accuracy. The maximal discrepancies were found to be around 6% which proves the efficiency of the present model.
Aymeric Lamorlette, Anthony Collin. Analytical quantification of convective heat transfer inside vegetal structures. International Journal of Thermal Sciences, 2012, 57, pp.78-84. ⟨10.1016/j.ijthermalsci.2012.02.010⟩. ⟨hal-01297730⟩
Journal: International Journal of Thermal Sciences
Experiments were carried out on reversed weak laminar inclined fountains to asses that unstable modes of round fountains are disturbed by the inclination. Indeed, compared to fountains developing on horizontal wall, some modes disappeared while others are split in several modes. This paper aims at describing and mapping these new modes regarding to the inclination and the inlet velocity. Explanations about what made the unstable modes evolve are also proposed. (C) 2011 Academie des sciences. Published by Elsevier Masson SAS. All rights reserved.
