A study on leakage-flow-induced vibrations. (3rd report. Moment of fluid-dynamic forces acting on the walls, one of which is vibrating with rotational mode).

Abstract

An analytical study is presented on leakage-flow-induced vibrations in the case of a one-dimensional, narrow, tapered passage. The moment of fluid-dynamic forces acting on the walls of the passage when one of them is vibrating in the rotational mode is determined. It is found that the area increment ratio, on which condition negative fluid-dynamic damping and negative fluid-dynamic stiffness can occur, changes remarkably with the location of the pivot. Negative fluid-dynamic stiffness can occur in the case of divergent and convergent passage. Negative fluid-dynamic damping is apt to occur in the case of divergent passage, but if the pivot is situated slightly behind the center of the passage, it can also occur in the case of convergent passage. If the pivot is situated at the inlet of the passage, negative fluid-dynamic stiffness and negative fluid-dynamic damping rarely occur.