On transition from pool fires to fire whirls inside a large compartment

Atrium full-scale fire tests have been conducted under symmetric and asymmetric opening distributions with different values of inlet air velocities. Circular flow patterns are formed around the flame, inducing fire hazardous phenomena, such as flame revolutions or fire whirls. Specifically, fire whirls have been observed in the case of asymmetric venting layouts. Subsequent numerical simulations of the tests have been performed with FDS. Sharp increase in the flame height, coupled to a noticeable tangential velocity circulation, has been correctly predicted during the appearance of fire whirls, which are in good agreement with the experimental measurements. A detailed numerical analysis of one fire test has been performed to analyse the fire whirls formed. The tangential velocity profiles have been observed to fit well to a Burgers vortex.