Investigation of the motion characteristics for a spring-mounted rotating cylinder in flow

Abstract

A spring mounted rotating cylinder placed in flow is investigated using a two-dimensional newly improved discrete vortex method at Reynolds number of 105. In this study, the non-dimensional rotation rate, $$\alpha$$ (rate of the cylinder surface velocity and flow velocity), varies from 0 to 16, and the reduced velocity $${\text{Ur}}$$, increases from 1 to 14. The relationship between the wake formation, hydrodynamics, and motion of the cylinder has been illustrated. Three different motions (VIV, reverse direction whirl, and same direction whirl) have been identified and illustrated. The VIV mainly occurs in the cross-flow direction, and it is generated at $$\alpha 3$$. The path of the same direction whirl looks like a slight round circle, and the moving direction is the same as the rotating direction. The frequency of the whirl is higher than that of the VIV at the same rotation rate. The same direction whirl starts from $$\alpha = 8$$ with $${\text{Ur}} = 13$$, and the frequency of this whirl increases with increasing rotation rate. Unlike that of the same direction whirl, the moving direction of the reverse direction whirl is opposite to the rotating direction, and the path of the whirl similarly seems to be a round circle. The reverse direction whirl is generated at $$2 \le \alpha \le 7.5$$. The frequency of the reverse direction whirl decreases with increasing the rotation rate due to the increased effective added mass. The relationship between the effective added mass coefficient and the rotation rate has been interpreted; the effective added mass coefficient remains steady at $$0 \le \alpha \le 1$$ then gradually increases at $$1 < \alpha < 2$$, and finally dramatically increases with increasing rotation rate at $$\alpha \ge 2$$.