CFD investigation of cross-flow effects on fire-wind enhancement

Investigation of fire-wind (fire cross-wind) interaction is highly instrumental in dissecting the potential effects of bushfire attacks on buildings. The increase of free-stream wind velocity downstream of the fire source due to the interaction of wind and fire is referred as fire-wind enhancement which has been recognized as one of the destructive consequences of bushfirewind interaction. Although occurrence of the fire-wind enhancement phenomenon has been reported in previous studies, the mechanisms and contributing factors affecting the phenomenon have not been reported in the literature. This study applies Computational Fluid Dynamics (CFD) technique to fundamentally investigate the effects of cross-wind on fire-wind enhancement. Fire-FOAM solver which is based on OpenFOAM platform was used to solve thermo-fluid governing equations. A module has been added to the solver to extract different components of flow acceleration and the corresponding fireinduced flow momentum. Experimental data of buoyant diffusion flame was used to validate the numerical model. A selected range of simulation scenarios with different free-stream wind velocities under constant fire intensity has been performed to identify the effects of free-stream wind velocity on fire-wind enhancement. The outcome of the research indicated that as a result of interaction of cross-wind and fire, a longitudinal (horizontal) favorable pressure gradient is generated which leads to enhancement of wind downstream of the fire. It was also shown that the normalized fire-induced pressure gradient decreases when free-stream wind velocity increases. Therefore, for constant fire intensity, the flow field with a higher free-stream wind velocity undergoes a lower enhancement.