Erosion Characteristics of Aluminum with Cavitating Jet and Collapse of Bubble Cloud

概要

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As for cavitating jets injected from an orifice nozzle of inner diameter 0.15 mm at pressure 10-200 MPa into still water at atmospheric pressure, we conducted experiments of flow visualization of free jets with high-speed CCD camera at 50×104 fps and erosion tests of aluminum specimens. From these experiments, the following results were obtained. In erosion tests of cavitating jets, it is known that there are two peaks in mass loss curves, and besides, the peak of the diameter of eroded area was found to exist between two mass loss peaks. The distance may be suited to cleaning material and peening on metal for large damaged area and controlling erosion effect by adjusting injection pressure. The mass loss of downstream peak owing to collapses of cavitation clouds was highest at certain pressure. A high pressure pulse wave was generated 1-5 μs before the volume of cavitation clouds becomes smallest, the incidence frequency was of the order of 10 kHz, and the propagation speed of pressure wave was 1000-1100 m/s. Cavitation noise and erosion could be caused by these behaviors of cavitation clouds.