Large Eddy Simulation of Naturally Induced Fire Whirls in a Vertical Square Channel With Corner Gaps

Abstract

Naturally occurring fire whirls are rare but highly destructive phenomena. These are mostly generated by the interaction between a buoyant fire plume and its surroundings. The whirling motion generated can enhance the plume length and sustain burning. In this paper, we report the results of a numerical investigation of whirling fires generated in vertical square channels with symmetric corner gaps. The numerical investigations of swirling fire plumes are used to analyze how the corner gaps alters the plume dynamics and combustion. An approximate (low Mach number) form of the Navier-Stokes equations is solved to calculate the mixing and transport of combustion products. Large scale eddies are directly simulated and sub-grid scale motion is represented with a Smagorinsky model. The current approach is based on a fixed heat release rate, regardless of the strength of the whirl generated by the corner slots. The effect of corner slot widths and their configuration on the swirling motion are studied systematically for a given channel geometry and fixed fuel-loss rate.