Numerical investigation of fire dynamics in the presence of burning obstacles under a unidirectional wind

Prediction of forest fire spread is challenging due to irregular distribution of fuel and unpredictability in the flow and combustion scenarios. The present study proposes a numerical approach to investigate a simplified problem of fire spread in the presence of burning obstacles under a unidirectional wind. Three-dimensional, turbulent, unsteady, incompressible flow calculations have been carried out using the Fire Dynamics Simulator. The turbulent flow is modeled using Large Eddy Simulation with a time marching scheme for the momentum transport. The effect of combustion and radiation are accounted for using source terms in the energy transport equation. Wooden obstacles that mimic shrub structures are placed in a computational domain of 6 x 1.5 x 2.26 m. Different cases, consisting of a single obstacle, multiple obstacles placed along and normal to the flow direction, are simulated with a uniform velocity of 3 m/s. The interactions between the flow dynamics and the flame fluctuations are analyzed from the three-dimensional flow and temperature field. The effect of spatial distribution of the obstacles on the fire dynamics are analyzed using time histories and spectra of velocity and temperature obtained from discrete Fourier transform of the unsteady data. The soot formation and its trajectory have also been analyzed.