Probing and Imaging of Vapor-Water Mixture Properties Inside Partial/Cloud Cavitating Flows

Experimental results of the void fraction, statistical chord length distribution (CLD), and bubble size distribution (BSD) inside and downstream of hydrodynamic cavities are presented at the laboratory scale. Various cavitating flows have been intensively studied in water tunnels for several decades, but no corresponding quantitative CLD and BSD data were reported. This experimental study is aimed at elaboration of a general approach to measure CLD in typical cavitating flows. Dual-tip electrical impedance probe (dtEIP) is used to measure the void fraction and CLD in different cavitation flows over a flat plate, including both supercavitation and sheet/cloud cavitation. For supercavitating flows, the void fraction of vapor is unity in the major cavity region. In contrast, the maximum void fraction inside the sheet/cloud cavitation region is less than unity in the present studies. The high vapor concentration region is located in the center of the cavity region. Based on the experimental data of CLD, it is found that the mean chord lengths are around 2.9-4.8mm and 1.9-4.4mm in the center region and closure region, respectively. The backward converting bubble diameters at the peak of BSD have similar magnitude, with probability density values exceeding 0.2. Empirical parameters of CLD and BSD are obtained for different cavity regions.