Numerical Analysis Of Flow Around A Circular Cylinder And Vortex Induced Vibration Of Riser

With the demand of oil continues to grow in the global society, oil exploitation will be a very important developing direction of industry in the future. Meanwhile with the amount of terrestrial oil field becomes less and less, offshore oil exploitation will inevitably be an important source of oil production in the future world, which means the trend of developing the offshore oil exploitation technique is irreversible undoubtedly. Marine riser system, which is the main component of ocean establishment, is a core technology of the offshore oil exploitation. It includes many job content during the whole process of offshore oil exploitation: input/output or circulating fluid, drilling or guiding the auxiliary line, reinjection fluid and so on. Regrettably the core technology of designing the marine riser system is mastered by a few countries such as the US, Norway and Japan, the national eleventh five-year plan clear and definite the determination to study and develop the technology of offshore oil production in China.Vortex-induced vibration(VIV) has always been a challenge during the study of offshore oil production over those years. Affected by variety of real complex ocean environment load, the wake region of marine riser will appear some vortex that generate and shed periodically, such vortex will generate a periodical lift force on the marine riser, which will lead the riser to vibrate in the transverse direction. Once the frequency of lift force action is close to the natural vibration frequency of the riser system itself, the riser will enter a state called “vortex-induced resonance”, which will accelerate the fatigue fracture of riser and cause the riser damage earlier, sometimes it even cause the oil spill accident. From which we can see that the research on the vortex-induced vibration of marine riser has an extraordinary significance on the offshore oil production.The classification of offshore-platform riser is firstly introduced, then this paper summarized the research progress of vortex-induced vibration in detail. Through the elaboration of basic flow characteristics of fluid and its control equation, this paper reveals the mechanism of vortex generation and shedding, also demonstrates vortex-induced vibration phenomenon essentially. By establishing the fluid flow equations: the famous Navier-Stokes equations. Then some numerical solution method for researching the vortex-induced vibration, which have been applied broadly in engineering, are introduced in detail. Especially for two broadly utilized turbulence models: RNG k ?? turbulence model and SST k ?? turbulence model. By calculating and analyzing two-dimensional transverse vortex-induced vibration of elastically mounted rigid cylinder, the more suitable turbulence model is obtained, the essential relation between the simulation results and vortex-induced vibration is analyzed deeply. Then with the help of Ansys and Fluent, three-dimensional vortex-induced vibration of riser is calculated and analyzed, by studying the relationship between structure parameter of riser and the response of vortex-induced vibration, this paper finally presented some research achievement which had certain reference value in the engineering practice.