Enhancing the aggressive intensity of a cavitating jet by introducing a cavitator and a guide pipe

In order to enhance the aggressive intensity of a cavitating jet for practical applications, such as cavitation peening, a nozzle equipped with an additional nozzle upstream from the main nozzle, i.e., a cavitator, and a guide pipe downstream from the main nozzle was proposed and optimized. The aggressive intensity of the jet was evaluated by the residual plastic deformation, i.e., the radius of curvature, in duralumin plate specimens subjected to the jet perpendicullary. The radius of curvature can be considered to be directly related to the aggressive intensity of the jet, as the plastic deformation such as introduction of compressive residual stress and/or work hardening in metallic materials is important parameters on cavitation peening. The deformation occurs because the pressure due to cavitation impacts is beyond the yield stress of the specimens. It was demonstrated that a nozzle equipped with an optimized cavitator and optimized guide pipe increased the aggressive intensity of the jet by a factor of 4.2 without an increase of the jet power, compared to the jet obtained with a conventional nozzle with neither cavitator nor guide pipe, as the cavitator fed cavitation nuclei for the jet and the guide pipe enlarged the cavitation clouds of the jet.