液体で満たされた回転体の不安定振動 : 回転体の縦横比の影響および不安定防止法

抄録

This paper deals with the self-excited vibration of a rotor completely filled with liquid. It is well known that a rotor partially filled with liquid undergoes self-excited vibration at a certain rotating speed, and that it is caused by the existence of the free surface of the liquid. In the present paper, it is shown experimentally that the self-excited vibration occurs even for a rotor completely filled with liquid, without any free surface. By visualizing the flow in the liquid, a secondary flow, large vortices, like the Gortler vortex, can be observed in an unstable state. The strict relationship between this secondary flow and the rotor instability may be quite difficult to calcify analytically; however, it is shown experimentally that this secondary flow has a great influence on the instability of the rotor. Experiments are performed with rotors of various aspect ratios. As the aspect ratio becomes large, the self-excited vibration occurs at a lower rotating speed, and the range becomes narrower. A stabilization technique is also investigated. It is suggested that several rings be placed around the rotor to avoid this kind of instability.