Local heat transfer enhancement around a matrix of wall-mounted cubes using passive flow control: Large-eddy simulations

The purpose of the research reported in this paper was to investigate the influence of attaching vortex generators (VGs) to a surface of a heated cube on flow structures and heat transfer using large-eddy simulation (LES). The cube was located in the middle of a matrix of similar cubes. Two kinds of vortex generators were investigated. The first kind was a simple rib extending in the span-wise direction (VG1) while the second consisted of several of small cubes (VG2). The flow and heat transfer around a cube with vortex generators were compared with the flow and heat transfer around a smooth cube. The LES results showed that the flow in the boundary layer around the cubes with VGs is more turbulent and unsteady than the flow around the smooth cube. More complex structures are generated close to the surface of the cube with VGs, resulting in a considerable increase in the heat transfer coefficient. Local overheating was found behind the rib-shape VG while even distribution of temperature was observed over the surfaces of the cube in the VG2 case. There was a 14% and 17% global increase in the heat transfer coefficient in the VG1 and VG2 cases, respectively.