Firebrand trajectory study using an empirical velocity-dependent burning law

Abstract

By the use of available experimental data on the burning characteristics of wood spheres with forced convection, a burning rate law has been obtained. By utilizing a constant drag coefficient model for a firebrand, trajectories have been obtained for firebrands in two fluid flow fields of interest in forest fire research. One ambient air flow field is the swirling turbulent natural convection plume, which approximates the velocity field above a fire whirl, a phenomenon which has been observed in the vicinity of large-scale forest fires. The second flow field examined is a tilted constant-velocity convection plume. In both cases, for some values of fire brand or plume parameters, trajectories were obtained which carried the the firebrands far from the point of release. These firebrands present a danger of initiating secondary forest fires far from the main conflagration.