Turbulent boundary-layer characteristics of compliant surfaces.

A hot-wire anemometer study was made of the turbulent boundary layer on a compliant coating. A compliant coated flat plate was made by covering a y^-in.-deep reservoir of fluid with a thin sheet of poly vinyl chloride. This compliant test plate which measured 26^ in. X 8^ in. was inserted flush in the floor of a low-speed wind tunnel. The hot-wire anemometer was used to measure velocity profiles, Reynolds stresses and turbulence intensity in the boundary layer. All tests were run at 38 fps and the skin tension, skin thickness, and reservoir fluid properties were varied during the tests. The universal velocity profile of the compliant coating indicated no change in mixing length from that of a hard plate but seemed to indicate a thicker laminar sublayer. The Reynolds stress and turbulence intensity were smaller for the compliant coating than for the hard plate and they seemed to correlate with previously measured skin-friction reductions.