5. Laser-induced fluorescence

K.S. Pervunin, A.Yu. Kravtsova, M.V. Timoshevskiy, K. Hanjalić
Kutateladze Institute of Thermophysics, Siberian Branch of the Russian Academy of Sciences (IT SB RAS), Russia, Novosibirsk State University (NSU), Russia, Delft University of Technology (TU Delft), Department of Chemical Engineering, the Netherlands

Validation and error estimation of velocity characteristics measured by PIV/LIF approach in a flow around a cavitating hydrofoil

Cavitating flows around a flat plate with rounded nose and a NACA0015 hydrofoil are investigated at different attack angles from 0 to 9 degrees by means of a PIV technique. A series of algorithmic approaches is given in the paper to process instantaneous PIV images. This type of flows is a sufficiently complex object to study that requires to apply sophisticated procedures of data validation. Utilizing such procedures allowed us to enhance substantially the quality of vector fields at the final step of processing. Performed analysis of measurement uncertainty of statistical quantities (the mean and turbulence characteristics) demonstrated a significant influence of the sample range on the uncertainty of measurement quantities. As a result, criteria for estimating an acceptable uncertainty of various quantities are also given in the paper. Thus, the PIV method was shown to be capable to measure velocity fields in cavitating flow, including the regions occupied by gas-vapor cavities. Analyzing distributions of the mean velocity and statistical moments of velocity fluctuations, it was revealed that the cavitation onset is caused by flow development of the carrier liquid near the foil leading edge. However, downstream the flow structure strongly depends on the cavitation pattern.
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