ON MODELING CAVITATION DAMAGE

The intensity of bubble collapse is defined as the power transmitted per unit surface area of the bubble when the collapse pressure is a maximum and is given by the square of the collapse pressure divided by the acoustic impedence of the liquid. The efficiency of damage is defined as the ratio of the intensity of erosion of the material to the intensity of bubble collapse. Quantitative analysis is made to show how this efficiency would be affected by various physical effects such as inertia, damping of gas and vapor inside the bubble, heat transfer, compressibility, surface tension and viscosity. Experimental results with vibratory apparatus show that the efficiency of damage is primarily controlled by the damping of non-condensible gases and vapor. At higher temperature viscosity also seems to be important. Within the range of experiments, surface tension of the liquids tested seems to be unimportant. The group of non-dimensional numbers derived from the above analysis as used to formulate a modeling technique to predict the rate of depth of erosion in actual operating hydrodynamic systems.