Numerical Investigation On The Mechanisms Of Vortex Induced Vibration Of Three Side-by-side Cylinders

The vortex-induced vibration(VIV)of multiple circular cylinders is widely observed in mechanical engineering and ocean engineering,such as the flows around marine risers,heat-exchanger tubes and transmission lines.Compare to the VIV of two side-by-side circular cylinders which has been intensively investigated for many years,the VIV of three side-by-side circular cylinders is more complicated due to the strong proximity interferences.Thus,carrying out investigations on VIV of three side-by-side circular cylinders to study the complex interaction between cylinders and wakes and to accurately predict the characteristics of responses is of great importance in both academic research and engineering application.This paper numerically investigated the vortex induced vibration of three side-by-side circular cylinders.After a comprehensive literature review on VIV of circular cylinder(s),a series of numerical simulations were carried out.These simulations cover several hot-spot issues,such as flow around three side-by-side stationary circular cylinders and the VIV of three side-by-side circular cylinders.The main findings is summarized below.i.Verification cases of flow around three side-by-side stationary circular cylinders were carried out.Good agreement has been achieved by comparing the present results with published data.ii.The near-wake patterns are significantly depended on the normalized spacing ratio.Within the range of spacing ratio investigated,six near-wake patterns were observed,i.e.,the single-bluff-body pattern,the biased gap-flow pattern,the first flip-flopping pattern,the second flip-flopping pattern,the in-phase synchronized pattern and the modulated pattern.iii.Numerical simulations of the VIV of three side-by-side circular cylinders in flow with the spacing ratio of T/D(28)2.0?2.5?3.0?4.0?5.0 and the reduced velocity of 2.0?U_r?10.0were carried out.The vibration responses and near-wake patterns were investigated to understand the underlying mechanism.iv.Seven near-wake patterns were observed in the VIV of three side-by-side circular cylinders,i.e.,the‘narrow-wide-narrow'pattern,the irregular pattern,the anti-phase synchronized pattern,the modulated pattern,the combined pattern,the in-phase synchronized pattern and the biased gap-flow pattern.This paper will greatly contribute to a deeper understanding on mechanisms of the VIV of three side-by-side circular cylinders.