A variant of a three-dimensional multiphase, physics-based model (Dahale et al., Int. J. Wildland Fire, in press) is used to analyze the effects of crosswind on flames generated from the burning of an isolated shrub. The shrub considered in this investigation is Chamise, found in abundance in chaparral vegetation and highly susceptible to bush fires. The shrub is represented as a porous medium comprising of branches and foliage. It is assumed that the thermal decomposition of the shrub results only in pyrolysis gases. The effects of moisture and char oxidation for the conditions investigated are assumed negligibly small, and hence neglected. Drag force arising due to the interaction between the solid and gaseous phases is modeled through the inclusion of source terms in the gas phase momentum equation. The mass and temperature of the solid phase are kept constant so that a statistically stationary state is reached. This approach makes a detailed statistical analysis of the flame and plume possible through time averaging. The source terms due to pyrolysis are included in the gas phase conservation equations. Radiative heat transfer is modeled by the discrete ordinates method. Turbulence is dealt with by large-eddy simulation with dynamic Smagorinsky subgrid-scale modeling. Subgrid-scale turbulent combustion is modeled based on a flame surface density concept proposed by Zhou and Mahalingam (Phys. Fluids, 2002). In this work, the shrub fires are modeled for cases with different wind speeds. In each case, the flow field generated due to the interaction of fire-induced flow field with the ambient flow field is studied. The second invariant of the velocity-gradient tensor is used to locate the various coherent structures formed due to the turbulent flow. A qualitative conclusion was made on the coexistence of the higher temperatures and turbulent kinetic energy in the flow. The regions of higher temperatures have lower turbulent kinetic energy and vice-versa.
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