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 θ 7300, and of thickness 6 over two axisymmetric bumps of height H = 6 and 26 and one symmetric bump of H = 26. LDV data were obtained at one plane, x/H ≥ 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