THREE-DIMENSIONAL NUMERICAL SIMULATION OF UNSTEADY TURBULENT NATURAL CONVECTION IN AN ENCLOSURE HAVING FINITE THICKNESS HEAT-CONDUCTING WALLS

Three-dimensional unsteady natural convection in a cubic enclosure having finite thickness walls subject to opposing and horizontal temperature gradient has been investigated by a finite volume method. The flow is driven by conditions of constant temperature imposed along the external surfaces of two vertical side walls while the remaining walls are adiabatic from outside. The turbulent flow considered into the volume is described mathematically by the 3D Reynolds averaged Navier-Stokes equations, including the time averaged energy equation for the mean temperature field. The Reynolds stresses appearing in the Reynolds equations have been calculated on the basis of the standard k-epsilon model with wall functions. Staggered grid procedure was used with a power law differencing scheme for the convection terms and central differencing scheme for the diffusion terms. The pressure-velocity coupling is achieved using the SIMPLER method. The velocity and temperature distributions were calculated at fixed Rayleigh and Prandtl numbers, Ra = 10(7), Pr = 0.7 and different values of the dimensionless time 0 <= tau <= 500.