Experimental study of vortex-induced vibrations of a cylinder near a rigid plane boundary in steady flow

摘要

In this study, the vortex-induced vibrations of a cylinder near a rigid plane boundary in a steady flow are studied experimentally. The phenomenon of vortex-induced vibrations of the cylinder near the rigid plane boundary is reproduced in the flume. The vortex shedding frequency and mode are also measured by the methods of hot film velocime-ter and hydrogen bubbles. A parametric study is carded out to investigate the influences of reduced velocity, gap-to-diame-ter ratio, stability parameter and mass ratio on the amplitude and frequency responses of the cylinder. Experimental results indicate: (1) the Strouhal number (St) is around 0.2 for the stationary cylinder near a plane boundary in the sub-criti-cal flow regime; (2) with increasing gap-to-diameter ratio (eo/D), the amplitude ratio (A/D) gets larger but frequency ratio (f/fn) has a slight variation for the case of larger val-ues of e0/D(e0/D 0.66 in this study); (3) there is a clear difference of amplitude and frequency responses of the cylin-der between the larger gap-to-diameter ratios (e0/D 0.66) and the smaller ones (e0/D < 0.3); (4) the vibration of the cylinder is easier to occur and the range of vibration in terms of Vr number becomes more extensive with decrease of the stability parameter, but the frequency response is affected slightly by the stability parameter; (5) with decreasing mass ratio,the width of the lock-in ranges in terms of Vr and the frequency ratio(f/fn)become large.