Study On Passive Jet Flow Control Of Oscillating Wake And Vortex Induced Vibration Of A Circular Cylinder

The circular cylinder is a common construction form in the engineering of structures such as bridge cables,chimneys,cooling towers,structures of offshore engineering,and marine pipelines.The flow around a circular cylinder involves flow separation,vortex generation,and shedding,which leads to vortex-induced vibration(VIV).The VIV not only causes long-term fatigue damage of the structure,but also results in a serious resonance effect that could instantly destroy the structure.Therefore,suppressing the oscillating wake of the circular cylinder and then eliminating the vortex-induced vibration is of great significance to improve the design and service life of a circular cylindrical structure.This paper presents a passive jet flow control method to suppress the oscillating wake of a circular cylinder based on a computational fluid dynamics(CFD)numerical simulation.Under the influence of the hollow pipes with jet holes where intake occurs in the front and blowing appears in the rear,the purpose of suppressing or eliminating the flow-induced vibration for a cylinder is achieved by overcoming the oscillating wake.The investigation mainly focuses on the effect for the pattern of jet holes and the arrangement distance along the spanwise direction for pipes.An optimal parameter scheme for suppressing the oscillating wake of a circular cylinder is then determined according to a comparison of the effect for aerodynamic forces.The optimization efficiency for amplitude is finally resolved in accordance with the numerical simulation of the VIV along the cross flow for the model supported by elastic mounting.The main contents of this paper are as follows:The numerical simulation for three-dimensional(3D)flow over a fixed circular cylinder under uncontrolled state was carried out.The 3D flow past a circular cylinder at a Reynolds number(Re)of 3900 was addressed based on different turbulence models.In order to validate the feasibility of the LES method and the numerical settings,the corresponding wind tunnel experimental and numerical results were adopted as references.On the basis of the LES method,three kinds of grid schemes were used to simulate 3D flow past a circular cylinder under Re=5.0×105.Moreover,in order to verify the accuracy of the grid scheme,the statistics of aerodynamic coefficients were used for comparing with the exiting experimental and simulated data.Based on the optimal grid scheme,the 3D flow past a circular cylinder with Re =1.0×10~4,3.0×10~4,5.0×10~4,7.0×10~4 and 9.0×10~4 were simulated numerically so that the present grid accuracy could be accurately proved to capture the characteristics of the flow field around a circular cylinder,which is the basis of further studies on suppressing the oscillating wake by using the passive jet flow control method.The numerical simulation for 3D flow over a fixed circular cylinder with the passive jet flow control pipe was carried out.The effect for the pattern of jet holes and the arrangement distance along the spanwise direction for pipes was mainly investigated.First,the effect of the passive jet flow control pipe on the aerodynamic forces and wake flow of a circular cylinder were studied at different directions,angles,and heights of the jet holes.An optimal holes mode of pipe for suppressing the oscillating wake was then determined according to a comparison of the effect for aerodynamic forces.Then,after determining the optimal holes mode,the influence of arrangement distance along the spanwise direction for pipes on aerodynamic forces and characteristics of flow field around a circular cylinder was studied.Finally,an optimal arrangement for the passive jet flow control pipe was defined.The numerical simulation for the VIV along the cross flow for a circular cylinder under uncontrolled and controlled measures was carried out.The numerical calculation model along the cross flow for a circular cylinder supported by elastic mounting was established.The VIV along the cross flow for a circular cylinder under uncontrolled state was investigated,and the maximum amplitude at resonance was obtained.The VIV along the cross flow for a circular cylinder with the passive jet flow control method was studied.Besides,the effect and the optimization efficiency for the amplitude were resolved.