Recent applications of near-wall, high-speed PIV for near-wall boundary layer characterization

Kurzfassung

The contribution will introduce a PIV implementation that combines high-magnification imaging, high-speed image capture and large samples counts in order to acquire long records of temporally coherent velocity data. For the investigation of turbulent boundary layers (TBL), the wall-normal velocity profile is captured using a narrow light sheet and reduced (narrow) camera field-of-view, such that sample counts beyond O(10E5) at sampling frequencies >10 kHz can be achieved. The PIV technique has been applied successfully in two recent EuHIT-funded projects that were performed respectively at the LML wind tunnel in May 2015 for the measurement of an adverse pressure gradient TBL and at the CICLoPE facility of Univ. Bologna in May 2016 for the measurement of fully turbulent pipe flow up to Re_\tau = 40,000. For both applications, details on implementation, sample results and lessons-learned will be presented. Ongoing developments are focussed on pushing the technique beyond 100 kHz using the latest generation of high-speed cameras and manufacturing-grade laser systems.