Numerical Investigation Of Vortex-induced Vibration Of Two Circular Cylinders In Tandem Arrangements In Oscillatory Flow

The vortex-induced vibration(VIV)of a circular cylinder is widely observed in many fields such as mechanical engineering,ocean engineering,etc.However,most of the researches were focused on the responses of the cylinder under steady and uniform flow conditions.This is far from the reality in ocean engineering in which wave plays an important role.In this paper,the vortex induced vibration of cylinders in oscillatory flow were carried out to understand the interaction between cylinders and wakes and to predict the characteristics of responses.It has a great importance in both academic research and engineering application.This paper numerically investigated the vortex induced vibration of an isolated cylinder and two in-tandem cylinders in oscillatory flow.After a comprehensive literature review,several hot issues in this area were addressed,such as the VIV of an isolated cylinder in oscillatory flow,oscillatory flow around two cylinders in tandem arrangement and the VIV of two in-tandem cylinders in oscillatory flow.The main research findings are listed below.?.Verification cases of oscillatory flow around an isolated cylinder were carried out.Good agreement has been achieved by comparing the present results with those published data.?.Numerical simulations of the VIV of an isolated cylinder in oscillatory flow with KC =5?KC = 10 or KC = 20 and the reduced velocity 1<Vr<11 were carried out.The vibration responses and near-wake patterns were investigated and the underlying mechanism was analyzed.?.Numerical simulations of oscillatory flow around two cylinders in tandem arrangement with G = 1.5.G=2,G = 3 or G = 4 and 1?KC?20 were carried out.A near-wake pattern map in the parametric space of G and KC was presented.It was found that for the cases with a small gap ratio,two cylinders behavior as an extended bluff body and the wake-shedding process is similar to that of an isolated cylinder.With increasing gap ratio,the interaction between two cylinders becomes stronger which results in a transversely spreaded vortex street in the gap of two cylinders.?.The numerical simulation of the VIV of two in-tandem cylinders in oscillatory flow with G = 2 was carried out.The drag and lift coefficients,vibration amplitude and frequency were investigated.Finally,the near-wake patterns of the VIV of two in-tandem cylinders in oscillatory flow were presented.The innovative results presented in this paper will greatly contribute to a deeper understanding on mechanism of the VIV of two in-tandem cylinders in oscillatory flow.