Large eddy simulation of the unstable flame structure and gas-to-liquid thermal feedback in a medium-scale methanol pool fire

Ahmed, Mohamed Mohsen; Trouvé, Arnaud

doi:10.1016/j.combustflame.2020.10.055

Cited by 34 publications

(7 citation statements)

References 28 publications

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“…In such cases, a decrease in the convective heat fluxes with decreasing grid size will occur around the centre of the pool fire and can potentially affect the numerical predictions if liquid evaporation is modelled. This aspect has been reported/discussed in the past by [43,67,73] in the context of pool fire modelling. A suggested guideline would be to avoid the calculation of the convective heat fluxes based on the first grid cell values as these approaches will be highly grid sensitive.…”

Section: Special Topic: Influence Of Grid Sizementioning

confidence: 74%

Review of Convective Heat Transfer Modelling in CFD Simulations of Fire-Driven Flows

Maragkos

Beji

2021

Applied Sciences

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Progress in fire safety science strongly relies on the use of Computational Fluid Dynamics (CFD) to simulate a wide range of scenarios, involving complex geometries, multiple length/time scales and multi-physics (e.g., turbulence, combustion, heat transfer, soot generation, solid pyrolysis, flame spread and liquid evaporation), that could not be studied easily with analytical solutions and zone models. It has been recently well recognised in the fire community that there is need for better modelling of the physics in the near-wall region of boundary layer combustion. Within this context, heat transfer modelling is an important aspect since the fuel gasification rate for solid pyrolysis and liquid evaporation is determined by a heat feedback mechanism that depends on both convection and radiation. The paper focuses on convection and reviews the most commonly used approaches for modelling convective heat transfer with CFD using Large Eddy Simulations (LES) in the context of fire-driven flows. The considered test cases include pool fires and turbulent wall fires. The main assumptions, advantages and disadvantages of each modelling approach are outlined. Finally, a selection of numerical results from the application of the different approaches in pool fire and flame spread cases, is presented in order to demonstrate the impact that convective heat transfer modelling can have in such scenarios.

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Section: Special Topic: Influence Of Grid Sizementioning

confidence: 74%

Review of Convective Heat Transfer Modelling in CFD Simulations of Fire-Driven Flows

Maragkos

Beji

2021

Applied Sciences

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“…The solver also features a radiation model based on a multi-phase radiative transfer equation (MRTE) that includes absorption/emission by the solid particles and by the gases (Consalvi et al (2002)); the MRTE is solved using the finite volume Discrete Ordinate Method (DOM) implemented in the OpenFOAM library. The radiation absorption/emission by the gases is modeled by either a Prescribed Global Radiant Fraction (PGRF) approach or a Weighted-Sum-of-Gray-Gases (WSGG) model (Ahmed and Trouvé (2021)). The PGRF approach is adopted in the present study in the flame region, while the absorption and emission in the plume region are calculated using Plank-mean absorption coefficients of CO2 and H2O.…”

Section: Vegetation Bed Modelmentioning

confidence: 99%

Large eddy simulations of the structure of spreading line fires at flame scale

Ahmed¹,

Trouvé²,

Forthofer³

et al. 2022

Advances in Forest Fire Research 2022

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Our general objective in the present study is to develop tools to better describe the coupling between solid phase and gas phase processes that control the dynamics of flame spread in wildland fire problems. We focus on a modelling approach that resolves processes occurring at flame scales, i.e., the formation of flammable vapors from the biomass vegetation due to pyrolysis, the subsequent combustion of these fuel vapors with ambient air, the establishment of a turbulent flow because of heat release and buoyant acceleration, and the thermal feedback to the solid biomass through radiative and convective heat transfer. The modelling capability is based on a general-purpose Computational Fluid Dynamics (CFD) library called OpenFOAM and an in-house Lagrangian particle model that treats drying, thermal pyrolysis, oxidative pyrolysis and char oxidation using a one-dimensional porous medium formulation that allows descriptions of thermal degradation processes occurring during both flaming and smoldering combustion. The modelling capability is calibrated for pine wood and is first applied to simulations of fire spread across a surrogate vegetation bed corresponding to thin, monodisperse, cylindrical-shaped sticks of pine wood with prescribed particle and environmental properties (i.e., bed height, surface-to-volume ratio, packing ratio, moisture content, and wind velocity). While the model can be used in sloped terrain, the present simulations are limited to a flat ground surface. The current emphasis is on determining threshold conditions for successful spread, differences between the plume-dominated and wind-driven flame regimes, possible transitions to a steady or time-dependent flame structure, and differences in the relative weights of the flaming and smoldering regions.

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“…LES of non-sooting and sooting fire plumes were reported in the literature with different levels of sophistication in the modeling of subrid-scale turbulence [4][5][6][7][8][9][10][11][12][13][14], turbulent combustion [14][15][16], radiative heat transfer [17][18][19], and soot modeling [16,20,21]. One of the difficulty in the modeling of the near field of fire plumes is that the flow, and the resulting air entrainment that controls the combustion process, is governed by the formation and growth of the flame base non-dissipative laminar instability near the edge of the pool that develops periodically to form energy containing large-scale toroidal vortices [22,23].…”

Section: Introductionmentioning

confidence: 99%

“…One of the difficulty in the modeling of the near field of fire plumes is that the flow, and the resulting air entrainment that controls the combustion process, is governed by the formation and growth of the flame base non-dissipative laminar instability near the edge of the pool that develops periodically to form energy containing large-scale toroidal vortices [22,23]. A consequence is that these instabilities have to be spatially-resolved which requires a grid-resolution of the order of 2 mm [12][13][14].…”

Section: Introductionmentioning

confidence: 99%

Large eddy simulation of fire-induced flows using Lattice-Boltzmann methods

Taha,

Zhao,

Lamorlette

et al. 2024

International Journal of Thermal Sciences

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Large eddy simulation of the unstable flame structure and gas-to-liquid thermal feedback in a medium-scale methanol pool fire

Cited by 34 publications

References 28 publications

Review of Convective Heat Transfer Modelling in CFD Simulations of Fire-Driven Flows

Review of Convective Heat Transfer Modelling in CFD Simulations of Fire-Driven Flows

Large eddy simulations of the structure of spreading line fires at flame scale

Large eddy simulation of fire-induced flows using Lattice-Boltzmann methods

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