Enhancement of an aggressive intensity of a cavitating jet by water flow holes near nozzle outlet

The cavitation cloud generated by submerged high-speed water jet has periodicity. The periodicity is provided by alternately repeating the bubbles generation and shedding process and cavitation nucleus filling process. Therefore, the construction of the filling process allows control of the shedding frequency of the cavitation clouds and may improve the aggressive intensity of the cavitating jet. In this paper, the water flow holes were provided at the nozzle throat outlet in order to form a stable and continuous filling flow. The aggressive intensity of this nozzle was compared by the mass loss of JIS A1050P. In addition, the cavitating jet was observed with a high speed video camera to confirm the characteristics of the jet. As a result, the mass loss per unit area increased as the diameter of the water flow holes increased. It is speculated that the enhanced flow around the cavitating jet due to the action of the water flow holes caused the increase in the damming pressure on the specimen. The increase in damming pressure increased the impact density and collapse impact force of the cavitation bubbles. Moreover, the large water flow holes resulted in stabilization of the shedding frequency of the cavitation clouds and growth scale. It may be a factor that the stable supply of cavitation nuclei to the cavitation main generation field was realized. However, since the water flow holes did not change the shedding frequency significantly, it is considered that the influence of the frequency on the aggressive intensity is small in this experiment.