Abstract
The double diffusive natural convection of smoke in a horizontal main flow was numerically studied at the Prandtl number Pr=0.71,the aspect ratio A=1,the Rayleigh number Ra=(10)^8 or (10)^9,the Lewis number Le=0.5,2 or 5 and the buoyancy ratio N=0.5,1 or 2. The smoke moves downward under the horizontal main flow at N>1 and upward at N<1. When the buoyancy ratio is unity, a double diffusive convection phenomenon occurred in the downstream. When the Lewis number is smaller or greater than unity, the smoke was disordered in the downstream or separated into the thermal and solutal convections. Then the lower side of smoke became disordered at Le>1 and the upper side became disordered at Le<1.
