Comparative measurements of wall shear stress characteristics in a zero-pressure-gradient turbulent boundary layer using multi-aperture defocussing micro PTV (MA-µPTV) and profile-PIV

Kurzfassung

The contribution provides details on the image evaluation of defocused triple particle images targeting the stream- and spanwise characteristics of wall-shear stress while mitigating deviations from self-similarity of triplet images through suitable calibration. Wall-normal profiles of 3c velocity statistics were obtained at a spatial resolution of 8 µm. Velocity statistics are consistent with profiles from high speed PIV and agree well to DNS/LES up to the fourth moment.Results indicate that MA micro PTV is a viable non-contact technique for measurements of the unsteady wall shear stress using only a single access port.