Numerical Simulation Of Vortex-induced Vibration Of Riser Model

The marine riser is an essential part for the development of marine resources.Because the ocean current is complicated in deep water environment,the riser will be subject to high temperature and high pressure,and then become particularly vulnerable.However,the vortex-induced vibration is one of the most common one among many factors,so it is necessary to study the VIV In this paper,DES turbulence model is used based on the CFD method,to conduct research on numerical simulation of different riser mode,and the concrete is divided into rigid cylinder model and flexible riser model.At first,research on numerical simulation was carried out to fixed single cylinder detour flow in this paper,to verify the feasibility of DES turbulence simulation when the detour flow is simulated;at the same time,it performed research on numerical simulation of threedimensional serial double cylinder detour flow with multiple spacing under different Reynolds number,to conclude the different coefficient and vortex shedding mode.Secondly,the research on the VIV of rigid cylinder was carried out.Fluid solid coupling simulation of double free VIV were respectively conducted to rigid cylinder with low mass ratio of 1 and 2.4 and high mass ratio of 7,and it concluded correlation between dimensionless amplitude and reduced velocity under different mass ratio condition,“8-shaped” movement track of cylinder,and phenomenon of beat and phase switch phenomena.etc.For rigid two circular cylinders in tandem,it conducted research on effects of spacing on the double cylinder double free VIV,to analyze rule of dimensionless amplitude changing with the reduced velocity in a proper order,and influence of spacing on the vibration characteristics,as well as vortex shedding condition and shedding change state at the tail flow area.In the end,research on the VIV of flexible riser with large aspect ratio was carried out.It studied that there are difference existed in inherent frequency of the riser,and the results showed that the inherent frequency in the water was less than that in the air;meanwhile,by using CFX+ANSYS software,it conducted the numerical simulation of fluid solid coupling for flexible riser VIV,and studied impact on flexible riser VIV under different shearing conditions based on research on rigid cylinder vortex vibration,to conclude the rule of riser vibration characteristic and vibration mode as well as vortex shedding release at tail flow area under different shear flow velocity;moreover,it further researched whether there are flow filed to cause influence on the vortex induced vibration characteristics inside the riser under the uniform flow condition.