Modeling and scaling laws for large fires

Abstract

Mathematical models of the convective transport induced by large fires are presented. The models are chosen to illustrate the role of scaling laws in the mathematical development and computer implementation of simulations. The basic equations governing large fire dynamics are presented in a form suitable for these studies. The role of vorticity and heat release is emphasized in this formulation. Two different fire scenarios are examined; each with a unique analysis aimed at the phenomena of interest. First, a "kinematic" approach to fire plume dynamics is used to relate vorticity and heat release distributions obtained from plume correlations to fire induced winds. The utility of this approach is illustrated by appeal both to experiments on individual laboratory plumes and simulations of mass fires. The interaction of fire plumes with atmospheric winds is illustrated by a smoke dispersion model that couples a simplified description of the stratified atmosphere with a CFD based simulation of the large scale fire induced motions. Simulations of crude oil fire plumes compared with large scale experiments are shown to demonstrate the use of this model. A brief discussion of additional factors involved in the analysis of large fires is outlined.