Numerical simulation of small area fires

Abstract

Plume dynamics and smoke injection into the atmosphere from large area fires ensuing a nuclear exchange are currently simulated by prescribed burns of smaller areas (radius < 1 km). The extent to which small area fire plumes accurately characterize those from larger urban fires (radius > 5 km) is not well established. A ‘large’ fire has a radius comparable to the stratification scale height of the atmosphere. Numerical simulations of smoke plumes and condensed-moisture clouds generated by small area fires are presented for three fire sizes and two ignition patterns for ‘average’ September Pacific Northwest atmospheric conditions. We find that the plume rise from small area fires is governed by the total heat release and entrainment, whereas that from large area fires is controlled primarily by the fire heating rate per unit area and the atmospheric stratification.