Wind-Aided Firespread Across Arrays of Discrete Fuel Elements

摘要

The rate of wind-aided firespread (v sub f) across an array of very-small-diameter, discrete fuel elements is sought, as a step toward predicting the advance in time of a firefront though either strewn debris in a heavily-blast-damaged scenario or through brush-and-grass-type wildlands. Here, the quasisteady rate (if one exists) is sought for conditions under which there is both (1) a wind whose mean speed U is constant and whose direction is constant, and (2) a horizontal bed with a macroscopically uniform fuel distribution. M is the mass of fuel (per unit planform area of the bed) consumed with firefront passage; here the fuel elements are thin, so the fuel consumed is identical with the fuel loading initially present, if fire propagates at all. Laboratory-scale experiments in a specially dedicated firetunnel, with supplementary approximate analysis, are reported. Extensive testing suggests that (v sub f) varies with sq root of U/m over a wide range of the parameters U and m. Only if the thin-fuel loading m approaches the rather large value of very roughly 2 g/sq cm is radiative transfer likely to play a role comparable to that of convection/diffusion for preheating. Keywords: Wind velocity; Fire storms; Nuclear explosion simulation; Flame propagation. (MM)