No abstract

Simulating interaction between forest fire and atmospheric processes requires a highly detailed and computationally intensive model. Processing this type of simulations in wildland fires forbids combustion-based models due to the large amount of fuels to be simulated in terms of quantity and diversity. In this paper, we propose an approach that couples a fire area simulator to a mesoscale weather numerical model in order to simulate local fire/atmosphere interaction. Five idealized simulation cases are analysed showing strong interaction between topography and the fire front induced wind, interactions that could not be simulated in noncoupled simulations. The same approach applied to a real-case scenario also shows results that are qualitatively comparable to the observed case. All these results were obtained in less than a day of calculation on a dual processor computer, leaving room for improvement in grid resolution that is currently limited to fifty meter.

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The purpose of this paper is both to present and validate the methodology of a hybrid method coupling a Eulerian and a Lagrangian approaches in turbulent gas-particle flows. The knowledge of the dispersed phase is displayed in terms of a joint fluid-particle probability density function (pdf) which obeys a Boltzmann-like equation. We chose two different ways of resolution of this equation, depending on the required level of description. The first one is a stochastic Lagrangian approach which embeds a Langevin equation for the fluid velocity seen along the particle path. The second one is a Eulerian second-order momentum approach derived in the same frame as the preceding one. These two approaches are then coupled through half-fluxes. This procedures allows well-posed boundary conditions stemmed from previous time-step statistics for the two approaches. The aim is to provide a methodology able to take into account physical phenomena such as particle bouncing on rough walls or deposition in inhomogeneous flows with a reasonable numerical cost. The paper present the methodology and validations in the case of inert monodispersed particle in a turbulent shear flow without two-way coupling. Comparisons of the results of the hybrid method with each approach and LES/DPS results indicate that the hybrid method could become a powerful simulation tool for gas-particle flows.