高雷诺数下海底悬跨管道绕流数值模拟
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摘要
海底悬跨管道所处工作环境恶劣,失效形式多样,涡激振动是导致其疲劳破坏的重要原因。为研究不同悬跨间隙比和海底流速对悬跨管道涡激振动强度的影响规律,利用Fluent软件进行了实管径高雷诺数下的二维绕流数值模拟,得到涡旋脱落形态,升力和阻力系数变化曲线。结果表明:海底悬跨管道的升力系数幅值和阻力系数均值随间隙比增大而减小,最后趋于稳定。在小间隙比情况下会出现因管道底部流速增大引起管道两侧升力极值不相等的现象;随海底流速的增加,升力系数幅值和阻力系数均值呈先增后减的趋势,规律与常规圆柱绕流一致;升力系数频率随速度增加而增大,受间隙比的影响较小。工程实际中,海底管道的铺设要尽量避免海流流速高和悬跨间距大的水域,对危险悬跨区段应设置涡激抑制装置。
Free spanning submarine pipeline work in the harsh condition and has many failure modes. Vortex-induced vibration is a significant cause leading to its fatigue failure. In order to study the law about different spanning clearance ratio and flow rate impacting on VIV strength of free spanning pipeline,this paper applied the software FLUENT to simulate twodimensional flow around actual diameter pipeline at high reynolds number and obtained the data about vortex shedding shape,lift coefficient and drag coefficient curves. The result indicates that: the lift coefficient amplitude and drag coefficient mean value of free spanning submarine pipeline decrease with clearance ratio increasing and gradually stabilize at last. In the case of small clearance ratio,lift extreme value is inequality on both sides of the pipe caused by the pipe bottom flow rate increasing. The lift coefficient amplitude and drag coefficient mean value present a trend of increasing first then decreasing with flow rate increaing,which is consistent with the conventional flow around a cylinder. Lift coefficient frequency increases with flow rate increaing and less affected by the clearance ratio. In engineering practice,water areas of high current velocity and large submarine spans should be avoid as much as possible to lay submarine pipelines and vortex-induced suppression device should be provided in danger sections.
Free spanning submarine pipeline work in the harsh condition and has many failure modes. Vortex-induced vibration is a significant cause leading to its fatigue failure. In order to study the law about different spanning clearance ratio and flow rate impacting on VIV strength of free spanning pipeline,this paper applied the software FLUENT to simulate twodimensional flow around actual diameter pipeline at high reynolds number and obtained the data about vortex shedding shape,lift coefficient and drag coefficient curves. The result indicates that: the lift coefficient amplitude and drag coefficient mean value of free spanning submarine pipeline decrease with clearance ratio increasing and gradually stabilize at last. In the case of small clearance ratio,lift extreme value is inequality on both sides of the pipe caused by the pipe bottom flow rate increasing. The lift coefficient amplitude and drag coefficient mean value present a trend of increasing first then decreasing with flow rate increaing,which is consistent with the conventional flow around a cylinder. Lift coefficient frequency increases with flow rate increaing and less affected by the clearance ratio. In engineering practice,water areas of high current velocity and large submarine spans should be avoid as much as possible to lay submarine pipelines and vortex-induced suppression device should be provided in danger sections.
引文
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[2]Raven P W J,Stuart R J,Bray J A,et al.Full-scale dynamics testing of submarine pipeline spans[C].Proceedings of 17th Annual Offshore Technology Conference.Houston,USA,1985:395-404.
[3]Tsahalis D T.Vortex-induced vibrations due wave-induced currents of a flexible cylinder to steady and near a plane boundary[J].Journal of Offshore Mechanics and Arctic Engineering,1987(109):112-118.
[4]Huse E,Nielsen F G,Soreide T.Coupling between in-line and transverse VIV response[C].Proceedinhs of the ASME 21st International Conference on Offshore Mechanics and Arctic Engineering-OMAE.Oslo,Norway,2002:835-847.
[5]Liang D F,Cheng L.Numerical modeling of flow and scour below a pipeline in currents Part I.Flow simulation[J].Coastal Engineering,2005,52(1):25-42.
[6]Yang B,Gao F P,Jeng D S,et al.Experimental study of vortexinduced vibrations of a pipeline near an erodible sandy seabed[J].Ocean Engineering,2008(35):301-309.
[7]李小超,王永学.稳定流作用下海底悬跨管线涡激振动研究[J].船舶力学,2012,16(7):797-803.LI Xiao Chao,WANG Yong Xue.Vortex-induced vibrations of free span pipelines exposed to steady currents[J].Journal of Ship Mechanics,2012,16(7):797-803(In Chinese).
[8]Fluent Inc.FLUENT User’s Guide[R].Fluent Inc.,2015:700-701.
[9]范平清,赵林林,邢彦锋.基于SST k-ω模型的汽车空调CFD仿真分析[J].机械强度,2014,36(4):587-591.FAN Ping Qing,ZHAO Lin Lin,XING Yan Feng.The CFD analysis of air conditioner based on SST k-ωequations[J].Journal of Mechanical Strength,2014,36(4):587-591(In Chinese).
[10]黄钰期,邓见,任安禄.钻性非定常圆柱绕流的升阻力研究[J].浙江大学学报:工学版,2003,37(5):596-601.HANG Yu Qi,DENG Jian,REN Ran Lu.Research on lift and drag in unsteady viscous flow around circular cylinders[J].Journal of Zhejiang University:Engineering Science Edition,2003,37(5):596-601(In Chinese).
[11]Molin B.海洋工程水动力学[M].刘永庚,译.北京:国防工业出版社,2012:100,2012:105,2012:107.Molin B.Hydrodynamique DES structures offshore[M].LIU Yong Geng,Jr.Beijing:National Defence Industry Press,2012:100;2012:105;2012:107(In Chinese).
[12]王美薇.海底悬跨管道振动分析及悬跨治理[D].大庆:东北石油大学,2014:36.WANG Mei Wei.Vibration analysis and suspended control of suspended pipeline in seafloor[D].Daqing:Northeast Petroleum University,2014:36(In Chinese).