Poiseuille flow-induced vibrations of a cylinder in subcritical conditions

摘要

Poiseuille flow-induced vibrations (PFIV, as a distinct type of vortex-induced vibrations, VIV) of a circular cylinder in subcritical conditions are numerically studied via a lattice Boltzmann method. A significant characteristic of the present PFIV model system is that the cylinder oscillation is excited by the Poiseuille-type fluid flow, rather than by the interaction of shedding vortices and structural elasticity for the classic VIV of an elastic structure. The effects of Reynolds number (10 = Re = 80), blockage ratio (0.4 = beta = 0.667) and mass ratio (0.25 = m* = 1024) on the behaviors of cylinders and fluid flows are investigated and special attention is paid to the critical phenomena. Based on the cylinder motion and the wake structure, three distinct regimes involving one steady and two vibration regimes are observed. For Re = 20, cylinder oscillation can be excited extensively in the branch of high blockage ratio. As beta is decreased below a critical value, the cylinder suddenly ceases to oscillate and rests at the channel centerline. For Re approximate to 20 with a high blockage ratio, the cylinder always undergoes large-amplitude vibration in the whole current range of mass ratio. When Re is increased, the phenomenon of critical mass ratio, beyond which large-amplitude oscillation ceases, is observed and the threshold decreases with increasing Re and decreasing) beta rapidly. By measuring the lift coefficient of a stationary cylinder placed at different transverse positions in a parallel-wall channel, the mechanisms for the observed phenomena are analyzed. (C) 2018 Elsevier Ltd. All rights reserved.