Numerical investigation of vortex-induced vibration of a circular cylinder in transverse direction in oscillatory flow

One-degree-of-freedom (1DOF) vortex-induced vibration (VIV) of a circular cylinder in oscillatory flow is investigated numerically. The vibration of the cylinder is confined in the cross-flow direction only. Reynolds-Averaged Navier-Stokes equations and k-omega turbulent equations are solved by a Petrov-Galerkin finite element method. Simulations are carried out for two Keulegan-Carpenter (KC) numbers of 10 and 20 and reduced velocities ranging from 1 to 36. It is found that the response contains only one frequency component as reduced velocity is less than 8 for both KC numbers and contains multiple frequency components as reduced velocity exceeds 8. All the frequency components are multiples of the frequency of the oscillatory flow except at a few reduced velocities. For KC=20, the vibration frequency components (or vibration mode) change frequently as reduced velocity is larger than 10. Wavelet transform is applied to analyse instant frequency components at a specific time instant. It was found that the change from one vibration mode to another is regular and periodic. Based on the wavelet transformation, a mode-averaging technique is proposed to identify all the frequency components that ever occurred in the vibration. The variation of amplitudes and frequencies of the vibration with reduced velocity is studied. (C) 2011 Elsevier Ltd. All rights reserved.