Estimation of aggressive intensity of a cavitating jet with multiple experimental methods

Abstract

An experimental study on the cavitating jet was conducted with emphasis placed on the detection of the energy that is emitted by the collapse of cavitation bubble. Four experimental methods, each respectively utilizing a hydrophone, an acoustic emission (AE) sensor, a laser Doppler vibrometer, and a polyvinylidene fluoride (PVDF) sensor, were compared. Aluminum specimens served as the target that would endure the impact of the cavitating jet. The mass loss was measured and the cumulative erosion rate was calculated. Various upstream pressures were used, and the effect of the cavitation number was considered as well. The results indicated that the cumulative erosion rate becomes maximum with the increase in the erosion time, and it is insensitive to variations in upstream pressure. The time span that is required for the cumulative erosion rate to reach its maximum value becomes shorter for high upstream pressures. An overall increase in the normalized energy is evident as the upstream pressure increases. At any given upstream pressure, the normalized energy varies inversely with the threshold level. The optimum threshold levels were obtained separately for each of the four methods. The correlation between the maximum erosion rate and the normalized energy was established statistically. The PVDF sensor proved to be the most effective instrument in estimating the aggressive intensity of the cavitating jet.