A NUMERICAL STUDY OF TURBULENT NATURAL CONVECTION IN A RECTANGULAR ENCLOSURE USING A TWO-EQUATION TURBULENCE MODEL

Abstract

Turbulent natural convection has been studied both numerically and theoretically. This work numerically studies turbulent natural convection in a rectangular enclosure with varying aspect ratios of 0.5, 1 and 2. The vertical walls of the enclosure are kept at a constant temperature difference of 10K while the horizontal walls are adiabatic. The work was carried for air as the fluid having a Prandtl number of 0.71. As the aspect ratio changed, the Rayleigh number changed from 108 to 1010, due to the changing length of the enclosure. The finite volume based solver Fluent with Boussinesq approximation was used to conduct the numerical study. The k-omega two equation Reynolds Averaged Navier-Stoke Equations - based turbulence model was used for turbulent simulation. The velocity contours, streamlines and isotherms for the different Rayleigh numbers are studied. The results obtained show that as the aspect ratio increases, eddies at the top of the hot wall and at the bottom of the cold wall increase and the flow on the two vertical walls tend to exert more force on the stratified core. With the increasing Rayleigh number it is evident that the flow becomes characterized by a thin boundary layer adjacent to the vertical walls and a virtually stagnant thermally stratified core.