This study reports the application of high-speed particle image velocimetry (PIV) to measure the mean and fluctuating velocity components in a turbulent boundary layer over a body of revolution. A narrow wall-normal strip of the flow field was captured using a synchronised high-speed laser and camera at a recording frequency of up to 80 kHz. The resulting high-speed PIV statistical quantities were shown to compare well with dual-pulse high-resolution PIV. The high-speed PIV streamwise velocity energy spectra were also found to compare well with hot-wire annemometry measurements at matched conditions.
Full-field velocity measurements offered by Particle Imaging Velocimetry (PIV) will represent a major capability enhancement within Australia's only large-scale Transonic Wind Tunnel (TWT). Until now, the application of PIV in Defence Science and Technology (DST) Group's closed-circuit TWT has not been attempted due to the potential risks posed to tunnel subsystems from the deposition of recirculating tracer particles. DST researchers have since examined tracer particle options through literature review, correspondence with operators of other TWT facilities, and pre-installation particle performance assessments conducted in the DST Low Speed Wind Tunnel (LSWT). Simultaneous 2D-PIV and aerosol particle sizing measurements have been collected for the assessment of five different seed materials including: 3 water-based particle mixtures, white mineral oil, and Di-Ethyl-Hexyl-Sebbecat (DEHS).The particle size distributions were then used to estimate particle response for future supersonic application in the TWT.
A performance study of several tracer particles for PIV has been conducted. The study included particle response time analysis of an oblique shock wave generated by a conical nose of a store model in a closed loop transonic wind tunnel, and in-situ measurements of the particle size distribution in a low-speed wind tunnel facility. From the oblique shock wave analysis, the estimated particle response time for different smoke materials and generator settings was of the order of 1.4 - 2.2 μs and the effective particle size was 0.58 - 0.85 μm, which was much larger than the measured geometric mean particle size. This larger size was mainly attributed to the correlation bias towards larger particles in PIV measurements. The effective particle size from the particle response time analysis accounts for the holistic performance of the PIV system. Additionally, particle response analysis was performed on ambient water droplets resident in the tunnel. The estimated particle response time for the water droplets was in the order of 3.4 μs and the effective particle size was 0.97 μm, revealing inferior performance compared to the smoke particles.
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