Complementary temperature-sensitive paint measurements and CFD analysis of wall heat transfer of cubes-in-tandem in a turbulent channel flow

The influence of cubes-in-tandem on wall heat transfer in turbulent channel flow is investigated using complementary methods of temperature-sensitive paint (TSP) measurements and computational fluid dynamics (CFD). Three systems-a single cube and cubes-in-tandem at spacing-to-span-wise widths (S/d) of 3 and 4-were comparatively studied. For the single cube, a high level of turbulence in opposite-circulation vortices occurred for significant augmentation of convective heat transfer. For the tandem system at 3d, circulation was periodically advected downstream from two symmetric vortices, in alternating fashion; this mechanism was found to promote a high heat transfer rate across the leading face of the downstream cube. When the spacing was increased sufficiently, i.e., 4d, a new horseshoe vortex system occurred for substantial enhancement along the front face of the downstream cube. As such, the system at 4d promoted a distinct flow field in the wake region of the downstream cube, which was responsible for larger augmentation of the heat transfer area. The results showed that the heat transfer was enhanced in the inter-body space of the system at 4d as compared with the single cube. Behind the downstream cubes, the enhancement of heat transfer was pertinent to the unsteadiness of circulation vortices; meanwhile, the heat transfer monotonically decreased by the stream-wise distance for the single cube.