LES study of the influence of the vortex generators on cooling of surface-mounted cubes

Abstract

The influence of vortex generators on the enhancement of heat transfer from a wall-mounted cube matrix was investigated by numerical simulation using finite-volume method. The momentum and convective heat transfer equations were discretized and solved using large-eddy simulation. The numerical simulation was performed on a fully developed turbulent flow over one cube mounted in the middle of a cube matrix. Constant heat flux was generated from the cubes. Periodic boundary conditions were applied in both the streamwise and the spanwise directions. In order to study the influence of vortex generator on the flow structures and heat transfer coefficient, the flow and the convective heat transfer equations were solved around two cube configurations: a smooth cube and a cube with vortex generator attached to its surface. The vortex generator used in this investigation is a simple rib attached to the top and the side walls of the cube close to the streamwise edge. The flow Reynolds number based on the bulk velocity and the height of the channel was 13000. Standard Smagorinsky subgrid-scale model was used to model the unresolved scales and heat fluxes. The LES results were compared with the experimental results and good agreement was obtained. Numerical flow visualization was used to provide a better insight into the flow structures and heat transfer coefficient around the cubes. The LES results showed that the flow in the boundary layer around the cube with vortex generator is more turbulent and unsteady than the flow around the smooth cube without the vortex generator. More turbulent structures are generated close to the surface of the cube resulting in a good mixing of heat and hence high heat transfer coefficient