LES simulation of terrain slope effects on wind enhancement by a point source fire

Abstract

Fire-driven flows associated with wind intervention can dangerously threaten buildings in bushfire-prone areas by increasing pressure load on the structures through fire-wind enhancement phenomenon. This phenomenon through which wind is enhanced by interacting with fire is exacerbated when the affected terrain is located in a positive slope area. This study employs LES simulations using FireFOAM platform to investigate the extent to which the wind enhanced by a point source of fire is affected by terrain slope. A module was appended to the FireFOAM solver to extract and output fire-induced forces and acceleration components for the analysis. The effects of terrain slope on wind velocity enhancement as well as the location at which local maximum wind enhancement occurs were studied. The LES results showed that with the increase of terrain upslope angle, wind enhancement along the centerline is significantly intensified, whereas local maximum wind enhancement that occurs at each side of the centerline is less affected. It was also shown that global maximum wind enhancement occurs immediately downstream of the fire source for all upslope angles. Moreover, similar to the local maximum wind enhancement, the rate of increase in global maximum wind enhancement reduces with the increase of terrain upslope angle. Keywords: Fire-wind enhancement, Point source fire, Terrain slope, Local and global maximum wind enhancement