A three dimensional CFD approach for deepwater riser VIV simulation
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This paper presents a computational fluid dynamics (CFD) approach for time-domain simulation of deepwater riser undergoing vortex-induced-vibrations (VIV). The flow field around the riser was solved by the unsteady, incompressible Navier-Stokes equations in conjunction with a large eddy simulation (LES) model. The fluid domain was discretized using overset (chimera) grids that allow for relative movement to accommodate the riser lateral deflections. The riser was divided into segments such that their instantaneous displacements are determined at each time step. The numerical scheme for the riser motion equation was presented, and its von Neumann stability was also investigated. The riser motion program was then integrated with the CFD codes for deepwater riser VIV simulations. Calculations were performed for a horizontally positioned riser with length-to-diameter ratio (L/D) =1400 under both the uniform and linearly sheared current conditions and compared with available experimental data. In general, the predicted VIV responses are in fairly good agreement with the corresponding measurements. For completeness, we also analyzed the VIV of a typical deepwater top tensioned riser in uniform current, and presented the detailed flow field and riser responses. The simulation results demonstrated that the present CFD approach is suitable for the VIV analysis of deepwater risers with large L/D and complex current conditions.
