Subgrid-scale fire front reconstruction for ensemble coupled atmosphere-fire simulations of the FireFlux I experiment

Costes, Aurélien ; Rochoux, Mélanie C. ; Lac, Christine ; Masson, Valéry

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This paper introduces the Blaze fire model based on a Eulerian level-set front-tracking method and solved using high-order numerical schemes. Blaze includes an original and efficient subgrid-scale fire front reconstruction to substantially reduce computational cost and better localize surface heat fluxes compared to a weighted-averaged method. In this study, Blaze is coupled to the MesoNH atmospheric model to evaluate its performance against the FireFlux?I experimental data set. Results show good agreement between simulations and measurements for both 25-m and 10-m atmospheric resolutions combined with a 5-m fire resolution. The fire-induced atmospheric flow below 10 m is correctly captured in the two-way coupled mode and leads to a realistic spread rate trend between the two instrumented towers compared to one-way forcing modes (forced and fire replay modes). A more realistic air temperature near the ground is obtained by considering heat fluxes in the already burnt area and not only at the flaming front. Also, the significant impact of inflow turbulence on both fire spread and fire-induced flow is highlighted. This study motivates the use of a statistical ensemble technique to account for near-surface turbulence and more generally, environmental variability at the scale of an experimental fire such as FireFlux I.</p>

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