Measurement of Wall Shear and Wall Pressure Downstream of a Honeycomb Boundary Layer Manipulator

摘要

A boundary layer manipulator in the shape of a honeycomb placed in a turbulent boundary layer has been shown experimentally to reduce local wall shear downstream by as much as 38% and wall pressure by 36%. The zone of measureable shear and pressure reduction extends for at least 300 pre-manipulator displacement thicknesses downstream. Pressure spectra of the manipulated flow scales better with inner-outer variables than does the unmanipulated flow. Convective pressure speeds are reduced by as much as approximately 30 % for Strouhal numbers above 0.3. Below Strouhal numbers = 0.3 convective phase speeds are not noticeably changed. This indicates pressure disturbances for Strouhal numbers < 0.3 may originate from the inner portion of the boundary layer since the manipulator scales are far larger than the viscous sublayer. Coherence appears to be reduced in the streamwise direction and increased in the spanwise direction. All tests were done in the same facility as in Blake using the same microphones and wall insert. Unlike his work and similar to the work of other more recent investigations peaks were found in plots of coherence vs. phase in the vicinity of Strouhal numbers approx. = 0.3. Keywords: Experimental data. (kr)