The primary characteristics of fire whirls in vertical square channels with a lateral seam

Abstract

A fire whirl is simply a vortex flow with combustion.To understand the mechanism generating fire whirls,large scale experiments were conducted in a vertical square channel(2.0 m × 2.0 m × 15.0 m) with a lateral seam.They were also simulated with computational fluid dynamics(CFD) using fire dynamics simulator(FDS) version 4.07 which includes a method for large eddy simulation.To investigate the primary characteristics of fire whirls,five cases were simulated,each using a different bottom vent.It was found that when three edges at the bottom of the channel connect with the ambient a fire whirl cannot be produced.The other four cases produced one.In those cases,the distribution rule of temperature and axial velocity of the fire whirl at the channel centerline with the changing of height was presented.Next,the observed shifting of the central axis of the fire whirl from the channel's centerline was analyzed.It was also noted that the positions of the top of the flame in the fire whirl were incontinuous.