Session MA - Turbulent Boundary Layers V.
MIXED session, Tuesday afternoon, November 23
Grand I, Westin Seattle
Stereo-PIV measurements were made on multiple planes in a turbulent boundary layer, including inclined cross-stream planes at \pm45^\circ to the streamwise direction, together with streamwise-wall-normal and streamwise-spanwise planes. The results show clear evidence of large-scale organization with long streamwise low-momentum zones consistent with the scenario of spatially coherent packets of hairpin vortices in the logarithmic region of the flow. Statistical correlation analysis across the boundary layer indicates the occurrence of a distinct two-regime behavior, in which streamwise-velocity-fluctuation correlation contours either appear to be coupled to the buffer region, or decoupled from it. The demarkation between these two regimes is found to scale well with outer variables. The results are consistent with a coherent structure that becomes increasingly uncoupled (or decorrelated) from the wall as it grows beyond the logarithmic region, providing additional support for a wall-wake description of turbulent boundary layers.