A Numerical Investigation of Cross Wind Effects on a Turbulent Buoyant Diffusion Flame

Abstract

The behaviour of a turbulent diffusion flame subjected to cross wind conditions is studied numerically using a finite-volume procedure. A k-∈-gRNG turbulence model and a ß-probability density function (pdf) are used for the description of the turbulent nonpremixed combustion process. The gas/soot radiation model used in the analysis is based on the PI-differential approximation method and coupled with a two-equation submodel for soot formation. This model is applied to methane/air flames for cross wind velocity ranging from 0.5 m/s to 2 m/s. For a moderate wind of 1 m/s, the transient behaviour of the flame associated with the development of buoyancy-driven large structures is examined. Under different windy conditions, numerical results show that the nature of instabilities which develop along the thermal plume, depends on the orientation of the density gradient with respect to the gravity. The wind effects upon the flame trajectories are analyzed from the angle of deflection between the hot gas stream and the wind direction. The numerical results are compared with an experimental correlation obtained for a pool fire. Temperature and soot concentration profiles are presented to illustrate how aerodynamic interactions may generate significant changes on received thermal fluxes, especially for leeward surfaces.