Numerical simulation of turbulent diffusion flame in cross flow

The effects of cross wind on the behaviour of a turbulent diffusion flame h ave been studied numerically. The multicomponent turbulent reacting flow is approached using a two-equation (k - epsilon) statistical model constructe d from the Favre averaging method. To improve the representation of turbule nt fields in fully developed and weak turbulent regions, RNG (Renormalizati on Group) k - epsilon turbulence modelling is adopted. Infinitely fast reac tion is assumed and the combustion rate is fully determined by the turbulen t mixing rate of fuel and oxygen using the Eddy Dissipation Concept (EDC). Energy lost by radiation is taken into account and soot formation is comput ed for the evaluation of the absorption coefficient of the soot-gas mixture using the gray gas assumption. Calculations have been performed both with and without wind. The numerical results show that the flow is characterized by oscillations which affect significantly the flame behaviour. The develo pment of shear buoyancy-driven instabilities (Kelvin-Helmholtz) results in the occurrence of large eddies in the thermal plume. As the cross wind velo city increases, a transition from buoyancy dominated flow to cross wind dom inated flow can be noted along with a reduction in oscillation amplitudes. The influence of cross dow on soot formation and the impact of the fire upo n leeward neighbouring surfaces are examinated over the 0. - 1.5 m/s cross flow velocity range.