A numerical analysis has been made for the buoyancy-driven turbulent thermal convection around a heat source in an enclosure. A hybrid model which is a hybrid of the k-ε model and the algebraic Reynolds stress model (ASM) is adopted. This model accounts for the non-isotropic turbulence due to buoyancy. The Navier-Stokes equations and energy equation, turbulent transport equations are solved with SIMPLER algorithm. The test is performed for the buoyancy-driven flow in a tall two-dimension cavity of 5:1 aspect ratio. The predicted results are compared with experimental data from Cheesewright et al. In the present work, it is found that the contribution of the ASM corrections to the shear stress is, close to the vertical walls, larger than that predicted by the k-ε model, while it is found that non-isotropic turbulence has a significant effect on shear stress near the heat source. Buoyancy jet which is driven by a heat source induces larger heat transfer rate on vertical walls than that on upper horizontal wall. It can also be seen that fluid flow containing energy which is generated in unstable region does not affect stable region fluid in case that the strength of heat source is comparatively weak.
