THE EFFECTS OF INCIDENCE ANGLE ON THE MEAN WAKE OF A SURFACE-MOUNTED FINITE-HEIGHT SQUARE PRISM

The wake of a surface-mounted finite-height square prism of sub-critical aspect ratio AR = 3 was studied experimentally in a low-speed wind tunnel at a Reynolds number of Re = 3.7x10(4). The ratio of the boundary layer thickness on the ground plane, to the width of the prism, was delta/D = 1.5. The incidence angle of the prism was varied from alpha = 0 degrees to 45 degrees. Wake mean velocity measurements were made in vertical planes normal to and parallel to the main flow direction using a seven-hole pressure probe. As the prism is rotated from alpha = 0 degrees to 45 degrees, the mean wake progressively widens and the maximum streamwise extent of the mean recirculation zone increases. The mean streamwise tip vortex pair is symmetric at 0 degrees and 45 degrees, but becomes strongly asymmetric at intermediate alpha, where the tip vortex is found higher above the ground plane on the wider side of the wake. The wake and tip vortex asymmetry is most pronounced near the critical incidence angle.