Numerical Simulation of Vortex-induced Vibration Characteristics of a U-groove Cylinder
In this study,the vortex induced vibration characteristics of bare cylinder and U-groove cylinders are systematically simulated based on the bidirectional fluid-structure interaction method with CFD and CSD,along with the overset grid method.We compare and analyze the effects of different circumferential positions of the grooves on the vibration response,vibration frequency,hydrodynamic coefficients and wake vortex shedding pattern.The reduced velocity range in which vortex-induced vibrations of the cylinder are suppressed or promoted by grooves at different circumferential positions is investigated.The results show that the 45° groove can effectively reduce the transverse vibration amplitude and lift amplitude of the cylinder in the range of low reduced velocity U*=2.0-8.0,whereas in the range of high reduced velocities U*=9.0-14.0,the 45° groove increases both the transverse vibration amplitude and lift amplitude of the cylinder.In the range of reduced velocities U*=7.0-11.0,the 90° groove significantly reduces the transverse amplitude of the cylinder.At reduced velocities U*≥12.0,the transverse amplitude of the 90° grooved cylinder progressively becomes larger than that of the bare cylinder,and the vibrational response exhibits mainly multi-frequency peaks and wide-band vibrational characteristics.When the transverse amplitude of the 135° grooved cylinder exceeds that of the bare cylinder,the root-mean-square variation of the lift coefficient and the mean drag coefficient are similar to those of the bare cylinder.Compared to the bare cylinder,the average drag coefficient of the 45°,90° and 135° grooved cylinder decreased by 28.39％,35.80％and 6.79％,respectively.Similarly,in the wake vortex shedding mode,SS,2S,2T and 2P modes were observed for the 45° and 135° grooved cylinders,while only 2C modes were found for the 90° grooved cylinder,without 2T and 2P modes.
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