vegFireFOAM v1.0: a Lagrangian vegetation-fire spread module for OpenFOAM

Abstract. Physics-based simulation of wind-driven vegetation fire requires consistent coupling among turbulent buoyant flow, gas-phase combustion, radiative and convective heating, moisture release, solid-fuel pyrolysis, char oxidation, and fuel-bed drag. Existing models mainly rely on structured Cartesian grids, extending the same coupled physics to body-fitted or unstructured terrain-resolved meshes within a modular, open-source framework remains a development need. We present vegFireFOAM v1.0, a vegetation-fire module for OpenFOAM/fireFOAM. Fuel particle is represented by Lagrangian multiphase parcels that exchange mass, species, enthalpy, momentum, and radiation with the carrier phase, using submodels for moisture release, devolatilisation, char oxidation, convective heat transfer, aerodynamic drag, and grey radiative absorption. Because the module couples through standard OpenFOAM finite-volume fields rather than a structured Cartesian mesh, the formulation can be applied to both grassland validation domains and body-fitted terrain configurations without modifying the parent solver. Fire spread therefore arises from resolved heat and mass transfer rather than from an imposed rate-of-spread closure. Evaluation uses completed, full-size simulations of two CSIRO grassland fires (C064 and F19) for quantitative validation, and a body-fitted ridge case for terrain-mesh demonstration. All three cases share the same vegetation thermochemistry and coupling options; case-specific fuel size, moisture, loading, and wind are supplied through dictionaries. For the grassland cases, least-squares fits to the filtered centerline fronts reproduce the experimental spread rates within 6.5 % for C064 and 3.9 % for F19, with coefficients of determination exceeding 0.999. The ridge calculation captures the expected slope-induced acceleration, giving a 21.2 % higher spread rate on the windward slope than on the post-crest plateau.