Unsteady heat transfer near a bluff body in contact with a moving wall

Results of a numerical study concerning two-dimensional time-dependent laminar flow near a square bluff body are reported. The configuration investigated is that of flow around a square block in contact with a moving wall, with fluid approaching the block parallel to the wall and at the wall speed. This geometry provides a two-dimensional model for the flow near a magnetic head-arm assembly flying over a rotating disk. Numerical calculations were also made for the case of flow past a square block adjacent to a fixed wall. The Reynolds numbers investigated ranged from 100 to 1000. Comparisons between the two calculated cases show that a moving wall exerts a significant destabilizing effect on the recirculation region behind a block, leading to a lower Reynolds number for the onset of flow unsteadiness. The vortex shedding phenomenon has been characterized in terms of the Strouhal number, and plots of Strouhal number versus Reynolds number are presented for the moving wall and fixed wall cases. Plots of the Nusselt number variation with time and Reynolds number are also presented