The fluid mechanics of fire whirls: An inviscid model

Abstract

Whirling fire plumes are known to increase the danger of naturally occurring or post-disaster fires. In order for a fire whirl to exist, there must be an organized source of angular momentum to produce the large swirl velocities as air is entrained into the fire plume. These vorticity-driven fires occur over a large range of length and velocity scales, and significantly alter the entrainment and combustion dynamics. A new model is derived for a buoyant plume that incorporates angular rotation and neglects dissipation; the result is a form of the steady state Euler equations. Included is a general solution for large density and temperature variations. Results are presented that identify the mechanisms and their effects toward creating a fire whirl.