Some Characteristics of a Two-Dimensional Starting Mass Fire with Cross Flow

Abstract

A numerical model which can be used to study some aspects of mass fires is presented. The k—ϵ model of turbulence and the flame sheet model of combustion are employed. To account for the “unmixed-ness” of the fuel and oxidant, a fraction of oxygen is treated as inert while radiative loss is modelled by assuming that a fraction of the locally released heat is lost by radiation. The source is taken as a 200 m wide strip constant source of mass in a uniform cross flow stably stratified atmosphere. The conditions assumed in this testing of the model are of the order encountered in large mass fires. Results indicate that although qualitatively the predictions are similar to those of a constant temperature source there are some significant differences, the most outstanding ones being: (1) a more defined downward “jet point” and upstream transition zone; and (2) high velocities within the source of the order reported in large mass fires. The main contribution of this effort is that a simple scheme can be used to study mass fire phenomena.