A discrete vortex analysis of flow around a vibrating cylinder with a splitter plate

Abstract

The mechanism of flow-induced vibration of a circular cylinder with a splitter plate was investigated by means of numerical simulation using the discrete vortex model. Since the splitter plate prevents interaction of the upper and lower separated shear layers, the interaction between the shear layers is not important, but the interaction between the flapping of the shear layers and the cylinder vibration is important. Consequently the lift on the cylinder fluctuates synchronously with the vibration frequency at any velocity. The phase lag between the lift on the cylinder and the displacement of the cylinder itself increases from 0 to π as the velocity increases. Therefore the aerodynamic damping is always negative and consequently the self-excited vibration can be induced at any velocity. It should be noted that in this case the aerodynamic damping estimated by the quasi-steady assumption is positive. The negative damping is caused caused by the vortex shedding and its reattachment to the splitter plate, which are synchronized with the vibration of the cylinder. The development and synchronization processes of the vibration of a cylinder without a splitter plate are also discussed.