Study on Cavitating Leakage-Flow-Induced Vibrations (Similarity and Observation of Leakage Flow for Occurrence of Self-Excited Vibration)

Abstract

This paper presents experimental studies on unstable vibrations of an axisymmetric body in a cavitating narrow annular passage. The self-excited vibrations caused by the cavitation occurred when the value of nondimensional pressure loss at the annular passage was about 0.16. This value corresponded to the similarity for the occurrence of unstable vibration because the value is determined by the annular gap, length of the leakage passage and Reynolds number. The leakage flow patterns containing the cavitation were observed in detail by changing the downstream pressure and the length of the leakage passaee. It was found that the self-excited vibrations occurred when the cavitation bubbles collapsed at close the outlet rather than the center of the passage. The vibrations of an axisymmetric body were stable when the cavitation bubbles disappeared in the vicinity of the inlet.