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

Abstract

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–ω 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.