Cavitation on a semicircular leading-edge plate and NACA0015 hydrofoil: Visualization and velocity measurement

Abstract

Using high speed visualization and particle image velocimetry (PIV), cavitating flows near a plane plate with a rounded leading edge and NACA0015 hydrofoil at angles of attack from 0° to 9° are studied. In the experiments, several known types of cavitation, as well as some differences, were detected with variation of the cavitation number. In particular, at small angles of attack (up to 3°), cavitation on the plate appears in the form of a streak array; on the hydrofoil, it appears in the form of individual bubbles. For the NACA0015 hydrofoil, isolated and intermittent streaks are divided and grow in regimes with developed cavitation; then, however, they merge in bubble clouds and form an extremely regular cellular structure. With an increase in the angle of attack to 9°, the structure of the cavitation cavity on the hydrofoil is changed by the streak structure, like in the case with the plate. In this work, it is shown that PIV permits one to measure the velocity in cavitating flows, in par ticular, within the gas vapor phase. It was established from the analysis of distributions of the average flow veloc ity and moments of velocity fluctuations that the cavitation generation is caused by the development of the car rier fluid flow near the leading edge of the hydrofoil. Down the stream, however, the flow structure strongly depends on the cavitation regime, which is seen from the comparison of the distributions with the case of a sin gle phase flow. The presented measurements qualitatively verify general trends and show some quantitative dis tinctions for the two considered flowpast bodies.

Numerical investigation of three-dimensional partial cavitation in a Venturi geometry

“…Both types of cavities have been studied, experimentally and numerically, to describe the physical mechanism, the internal structure of cavities, the turbulence-cavitation interaction and to investigate the transition from quasi-stable to cloud cavitation. [2][3][4][5][6][7][8][9][10] Two main mechanisms have been identified for the break-off cycles: the development of a liquid re-entrant jet and the propagation of pressure waves created by the cloud collapses. [11][12][13][14][15] The structures of partial cavities have a fully three-dimensional topology as observed on hydrofoils with high-speed imaging method.…”

3D Cavitation Shedding Dynamics: Cavitation Flow-Fluid Vortex Formation Interaction in a Hydrodynamic Torque Converter

“…Most of their research focuses on experimental observation and performance testing, but only a few reports are available on the cavitation mechanism and transient cavitation behavior of hydrodynamic torque converters. Microwave telemetry, nearfield acoustic measurement, and particle image velocimetry can be employed to predict the cavitation formation and process in a hydrodynamic torque converter [11][12][13][14][15][16][17]. Nearfield acoustic measurement has been employed to directly detect the cavitation effect of the flow field in a hydrodynamic torque converter with different blade geometries [18][19][20].…”

Numerical investigation of three-dimensional partial cavitation in a Venturi geometry

“…In opposite, cloud cavitation is a highly unsteady phenomenon presenting a periodically varying length that is associated to the large shedding of vapor clouds. Both types of cavities have been studied, experimentally and numerically, to describe the physical mechanism, the internal structure of cavities, the turbulence-cavitation interaction and to investigate the transition from quasi-stable to cloud cavitation [2][3][4][5][6][7][8][9][10] . Two main mechanisms have been identified for the break-off cycles: the development of a liquid re-entrant jet and the propagation of pressure waves created by the cloud collapses [11][12][13][14][15] .…”