Cavity length and re-entrant jet in 2-D sheet cavitation

Abstract

Some features of hydrodynamic cavitation have been investigated in this experimental study to understand the role of the re-entrant jet in the formation of sheet (or cloud) 2-D cavitation. Velocity profiles, frequency contents of the cavity, pressure coefficients and pressure pulses spectrum have been measured in isothermal conditions. Physical quantities of interest were found to be greatly affected by the rate of pressure increase. Flow separation, surge instability, hysteresis, rebounds, splashes, choking and re-entrant jets have been observed. A correlation has been found between the cavitation number and the cavity length. The frequency content was detected by a new method that produces a spectrum at high Strouhal numbers. A large band without a peak was observed for the highest frequencies, e.g. greater than 1000 Hz. The role of the re-entrant jet in breaking the cavity was not found to be as much important as it is currently believed. The present results, obtained through thousands of experiments, may be of interest to predict cavity formation. © 2006 WIT Press.