Reynolds and Mass-Damping Effect on Prediction of the Peak Amplitude of A Freely Vibrating Cylinder

摘要

The Reynolds effect and mass-damping effect on the peak amplitude of a freely vibrating cylinder is studied by using forced oscillating data from Gopalkrishnan's research in 1993, in which all experimental cases were carried out at a fixed Reynolds and the tested cylinder was recognized as a body that had no mass and damping. However, the Reynolds and mass-damping are the very important parameters for the peak amplitude of a freely vibrating cylinder.In the present study, a function F is introduced to connect the forced oscillation and free vibration. Firstly the peak amplitude A*G can be obtained from the function F using forced oscillation data of Gopalkrishnan's experimental at Re=104, and then the Reynolds effect is taken into account in the function f(Re), while the mass-damping effect is considered in the function K(α), where α is the mass-damping ratio. So the peak amplitude of a freely vibrating cylinder can be predicted by the expression:A*=K(α)f(Re)A*G. It is found that the peak transverse amplitudes predicted by the above equation agree very well with many recent experimental data under both high and low Reynolds conditions while mass-damping varies. Furthermore, it is seen that the Reynolds number does have a great effect on the peak amplitude of a freely vibrating cylinder. The present idea in this paper can be applied as an update in the empirical models that also use forced oscillation data to predict the vortex induced vibration (VIV) response of a long riser in the frequency domain.