Study of vortical separation from three-dimensional symmetric bumps

Surface mean pressures, oilflow visualization, and three-velocity-component laser Doppler velocimeter (LDV) measurements are presented for a turbulent boundary layer of momentum thickness Reynolds number, Re-theta approximate to 7300, and of thickness 6 over two axisymmetric bumps of height H = delta and 2delta and one symmetric bump of H = 2delta. LDV data were obtained at one plane, x/H greater than or equal to 3.26, for each case. Complex vortical separations occur on the lee side and merge into large streamwise mean vortices downstream for the two axisymmetric cases. The near-wall flow (y(+) < 90) is dominated by the wall. For the axisymmetric cases, the vortices in the outer region produce large turbulence levels near the centerline and appear to have low-frequency motions that contribute to turbulent diffusion. For the case with a narrower spanwise shape, there are sharper separation lines and lower turbulence intensities in the vortical downstream flow.