Evaluating dynamic pressure measurements within the turbulent boundary layer of drag reducing surfaces

Laboratory scale evaluation of various drag reduction surface morphologies can provide valuable insight on their capabilities for both design optimization and as-built performance verification. Specifically, the primary drag reduction technique evaluated here is the implementation of riblet surfaces which refers to small scale, streamwise structures which tailor the turbulent boundary layer to reduce viscous drag. Various techniques, including velocity profile surveys and direct measurement of shear force, have been developed but often involve significantly complex calibration procedures. In an effort to streamline small-scale testing of candidate surfaces, a boundary layer pressure rake has been implemented along with unique remote-pressure-measurement reconstruction techniques to understand dynamic pressure fluctuation behavior. Results of these measurements are compared to direct measurement of shear via force balance.