Study on Mechanism for Unstable Vibrations of an Axisymmetric Body in a Cavitating Leakage Flow

An axisymmetric body in a cavitating narrow annular parallel passage attains the self-excited vibrations when the apparent passage formed by the cavitation bubbles becomes certain conditions. This paper presents experimental and analytical studies on the mechanism for such unstable vibrations. In order to examine the apparent passage, the cross-sections of the leakage flow containing the cavitation are observed in the one-dimensional leakage model. When the self-excited vibrations occur, the cavitation bubbles disappear in the vicinity of the exit. Relating these apparent passages to the annular passage, the fluid-dynamic forces acting on an axisymmetric body are investigated theoretically. The theoretical results show that the fluid-dynamic damping is negative when the unstable vibrations occur experimentally.