SIMULATION OF TORNADO - LIKE HEAT TRANSFER AT THE FLOW PASSING A RELIEFWITH DIMPLES
The mechanism of eddy enhancement of heat transfer process over a surface with hemispherical dimples is investigated using Reynolds equations written for Cartesian velocity components for incompressible viscous fluid flow. Low-Reynolds number k-ω zonal Menter's model is applied to describe the turbulent effect. This model is modified with taking account the curvature of the streamlines by the approach of Rodi-Leschciner and Hirsh. The solving of the governing equations is carried out by implicit factorised algorithm including the
convenient calculating procedure SIMPLEC. The numerical investigations of the laminar and turbulent flow passing shallow cavity on the flat plate have demonstrated the generation of two-cells symmetrical vortex structure within the lonely dimple. The lateral deformation of the dimple caused the appearance of the single large-scale eddy structure, which for the case of the deep dimple increased the heat transfer. The new many parametrical dimple shape has been proposed. It was combined from two dimple halves with smooth edges and
cylindrical insertion of determined length. These dimples were placed at the given angle of attack to the oncoming flow and due to this the heat transfer from the wall was increased. The heat transfer augmentation by vortex structures generated within the dimples designed on the wall of a narrow channel of constant as well as variable cross section has been achieved. The effect of a number of dimple rows (the number of dimples were 15) on heat transfer enhancement has been discovered. The heat duty of the flat channel wall augmented by
hemispherical dimples (the step between the dimples was equal 1,155 of dimple diameter) at Re=6000 has been enlarged in 1,6 times in comparison with the one for the smooth wall.