Assessment of ForeFire/Meso-NH for wildland fire/atmosphere coupled simulation of the FireFlux experiment

Abstract

Numerical simulations using a coupled approach between Meso-NH (Non-Hydrostatic) LES (Large Eddy Simulation) mesoscale atmospheric model and ForeFire wildland fire area simulator are compared to experimental data to assess the performance of the proposed coupled approach in predicting fine-scale properties of the dynamics of wildland fires. Meso-NH is a non-hydrostatic, large eddy simulation capable, atmospheric research model. ForeFire insures a front tracking of the fire front by means of Lagrangian markers evolving on the earth’s surface according to a physical rate-of-spread model. The atmospheric model forces the fire behavior through the surface wind field, whereas the fire forces the atmosphere simulation through surface boundary conditions of heat and vapor fluxes. The FireFlux experiment, an experimental 32Ha burn of tall grass instrumented with wind profilers and thermocouples, was designed specifically to estimate the atmospheric perturbation introduced by wildland fire. Comparisons of the simulations at different resolutions with the large-scale experiment validate the chosen coupling methodology and the choice of a coupled approach with a meso-scale atmospheric model for the prediction of wildland fire propagation. Distinct fire propagation behavior is simulated between coupled and non-coupled simulation. While the simulations did not reproduce high frequency perturbations, it is shown that the atmospheric model captures well atmospheric perturbations induced by combustion at the ground level in terms of behavior and amplitude.