Three Dimensional Numerical Simulation of Vortex Induced Vibration For a 500-m-long Marine Riser

Wang, Jiasong (School of Naval Architecture, Ocean and Civil Engineering, Shanghai Jiao Tong University) | Zhan, Lulu (School of Naval Architecture, Ocean and Civil Engineering, Shanghai Jiao Tong University) | Wang, Chenguan (Key Laboratory of Power Machinery and Engineering, Shanghai Jiao Tong University) | Jiang, Shiquan (CNOOC Research Center, China National Offshore Oil Corp (CNOOC)) | Xu, Liangbin (CNOOC Research Center, China National Offshore Oil Corp (CNOOC))

OnePetro 

ABSTRACT:

A three dimensional vortex-induced-vibration (VIV) fluid-structureinteraction (FSI) simulation for a 500-m-long marine riser is presented in this paper. The simulations were implemented by solving the unsteady Reynolds Navier-Stokes equations and the k-ω turbulence model coupling with the dynamic response equation. A good agreement was achieved by modeling an available experimental VIV problem. Several cases of VIV simulations for actual size of a marine riser, 0.5334 m in diameter and 502.92 m in length with different top preloads were carried out to address the control of VIV. The obtained results indicate that large, unsymmetrical and bending deformations appear to the riser, the riser vibrates with multi-mode, and the in-line dynamical response should not be ignored. When exerting a proper preload, the vibration amplitude is reduced remarkably and the excited mode number is reduced as well, which reflects that exerting preload is a good manner to suppress the VIV of long marine riser.



INTRODUCTION


Vortex shedding due to flow around a fixed or oscillating cylinder exists widely in a lot of real practical engineering, especially in the offshore engineering. Vortex induced vibration (VIV) analysis plays a leading role in determining the life span of marine risers, which may be considered to be an important source of failure of marine riser in the offshore industry. With the development of deepwater oil exploitation, the need to enhance our knowledge about VIV of risers with considerably large aspect ratio of length to diameter has greatly risen. A better comprehension of VIV for risers in real ocean conditions is necessary. From the multi-physics point of view, when fluid interacts with a solid structure, fluid-structure interaction (FSI) will occur, then exerting pressure varying periodically to the structure. As a result, it leads to time-varying deformation of the flexible structure, and then alters the flow field conformation.