Efficient Profile Sensor based on High-Speed PIV

Abstract

A high frame rate camera and a continuous wave laser are used to capture long particle image sequences exceeding 30,000 consecutive frames at framing frequencies up to 20 kHz. The combination of large image number and high frame rate is possible by restricting the field of view to a narrow strip of 256 pixel width and 1024 pixel height. The electronic shutter of the high-speed CMOS camera is reduced to 20us to prevent excessive particle image streaking. Multi-frame PIV processing algorithms are employed to improve the dynamic range of recovered PIV data. The large number of velocity data permits a reliable estimation of both the mean velocity profile down to a few wall units as well as statistical information such as the near wall Reynolds stress components. The measurement technique is demonstrated on a turbulent channel flow inside a small wind tunnel with Re_delta = 4300 and Re_tau = 220. The continuous velocity data can further be used to extract frequency spectra and probability density functions of the boundary layer flow.