Numerical investigation of streamwise vortex-induced vibration of a rotating cylinder subjected to an oscillatory flow

Abstract

Vortex induced vibrations of a rotating cylinder placed in an oscillatory flow are investigated using two-dimensional numerical simulations at a Reynolds number of 150. The cylinder was allowed to undergo undamped vibrations only in the streamwise direction, with a constant mass ratio of m* = 2 and a range of reduced velocities from V_r = 1 to V_r = 20. Simulations were carried out for two Keulegan-Carpenter numbers of Kc = 5 and Kc = 10, with the non-dimensional rotation rate of the cylinder varying from α = 0 to α = 1. With an increase in V_r, the vibrational amplitude initially increased to reach a peak value in the lock-in range, beyond which it decreased. The rotation led to a higher peak value of the vibrational amplitude and this phenomenon was more prominent at Kc = 10. For both Kc = 5, 10, rotation rates greater than α = 0.5, 0.7, respectively, caused a secondary increase in the vibrational amplitude as V_r increased beyond the lock-in range. The fast Fourier transform analyses of the in-line force coefficient, and the in-line velocity were performed to highlight the influence of rotation on vibration frequencies and shedding patterns. The vortex shedding patterns showed that the wake flow patterns differ from the typical flow regimes observed for a non-rotating and non-vibrating cylinder. The effective Keulegan-Carpenter number, based on the relative velocity of the oscillatory flow and the vibrating cylinder, did not play a significant role in the formation of different flow regimes, and the transition between the regimes was found to be very irregular.