Effect of nozzle geometry on a standard cavitation erosion test using a cavitating jet

In order to accurately and reliably evaluate the cavitation erosion resistance of materials using cavitating jet apparatus according to ASTM G134, the effect of various types of nozzle geometries on the erosion rate was investigated. As the erosion rate depends on the erosion time and the distance from the nozzle to the specimen, i.e., the standoff distance, the mass loss as a function of erosion time at the optimum standoff distance was measured. It was shown that the erosion rate depended on the nozzle geometry. In fact, the aggressive intensity of the cavitating jet I_J depends on the nozzle geometry. When a cavitating jet of low I_J was used in the erosion test, it took some time to reach the maximum cumulative erosion rate E_Rmax, which is recommended in ASTM G134 as a parameter for determining the cavitation erosion resistance of materials. In the present experiment, the difference in E_Rmax was more than 600%, and the time required to reach E_Rmax was also scattered over 600%, for the different nozzles used. It was also revealed that E_Rmax could be obtained from the product of I_J and the reciprocal of the relative cavitation erosion resistance of the material, R_ER.