Numerical analysis of point source fire on fire-wind enhancement

Fire-wind enhancement phenomenon is referred to as an increase of wind velocity through interacting with fire. Wind enhancement during bushfire attacks can significantly increase pressure load on buildings and consequently pose a threat to the structures built in bushfire prone areas. The aim of this work is to study the effects of point source firesize on fire-wind enhancement. For this purpose, the large eddy simulations (LES) are performed for different fire-wind interaction scenarios. The simulations are conducted using FireFOAM solver which is an opensource C++ computational fluid dynamic (CFD)
platform. A module is implemented to the solver to extract individual fire-induced force fields generated due to the fire-wind interaction. The effects of fire source size under two different conditions are investigated, namely, constant fire intensity (fire heat release rate per unit area) and constant fire heat release rate. The results reveal that increasing the size under constant fire intensity amplifies the fire-induced negative pressure gradient and causes a stronger wind enhancement. The LES results for different fire size while the fire heat release rate is constant show that the wind enhancement does not substantially change along the fire plume centreline downstream of the fire source. However, maximum wind enhancement, being formed symmetrically at the two sides of domain centreline, significantly reduces for the larger fire source size. The results also show that in both constant fire intensity and constant heat release rate conditions, the region of wind enhancement is expanded with the increase of fire source size.