Effect of Pressure on the Length of Cavity and Cavitation Damage Behind Circular Cylinders in a Venturi

Abstract

The effect of pressure on the length of cavity and cavitation damage is investigated with a venturi for cavities in water behind circular cylinders. The pressure range covered is 2.45 kgm/cm2 to 5.50 kgm/cm2 gage. Damage data are obtained for two sizes of cavitation sources of diameters 1.90 cm and 2.22 cm. Damage increased to a peak and decreased further with decrease in pressure. The studies on the length of cavity were extended to eight source diameters ranging from 0.95 cm to 3.18 cm. The increase in the length of cavity was slow up to about the length equal to 3 to 4 diameters and was rapid thereafter with decrease in pressure. The influence of test section boundaries on the phenomenon was investigated by observing the incipient, desinent, and choke cavitation conditions for fourteen blockage ratios ranging from 0.09 to 0.50. The boundary effects were less significant for blockage ratios less than 0.30. Attempts for unified correlations of the observed data by using weight loss at the beginning of steady-state zone corresponding to a maximum weight-loss rate in correlating the normalized volume of erosion with the normalized cavitation parameter, indicated peak damage at the same value of the normalized cavitation parameter.