Attenuation of swirling motion of a fire whirl in a vertical shaft

Abstract

Experiments on fire whirls generated by a gasoline pool fire in a vertical shaft were carried out. Vortex motions of swirling flame induced by buoyancy above the pool fires were observed to be more vigorous with increase in height. Upward flame motions were resulted due to increase in buoyancy. The phenomenon was described mathematically by solving the vorticity transport equation with reasonable assumptions and appropriate boundary conditions. Analysis gave swirling attenuation along the vertical direction. By measuring heat release rates and fire whirl diameters at different heights, vertical variation of circular speeds of fire whirls was derived.