Fire Plume in a Sharply Stratified Ambient Fluid

Abstract

The present work analyses theoretically and numerically fire plumes evolving in a two-layer stratified environment. The ambient fluid consists of a lower cold (heavy) layer and an upper warm (light) layer with a sharp interface. The fire plume is controlled by the fire heat release rate Q. Depending on the density interface location, the temperatures of the layers and on the fire source conditions, the fire plume can rise indefinitely or can be captured by the density stratification. To determine a criterion between these two situations, a theoretical model is proposed. With this model, it is found that the trapping/escaping criterion of the fire plume is determined in terms of a stratification parameter \(\varLambda > 0.88\). This stratification parameter \(\varLambda\) is a function of the fire heat release, the density interface location and the ambient stratification. The model also allows the plume height to be determined analytically. The comparison with the numerical data shows an excellent agreement. Finally, for practical purposes, we propose a simplified correlation to estimate the height of the trapped plume as a function of the interface height, the temperatures of the layers and the fire heat release rate.