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Vortex-induced vibrations of piggyback pipelines near the horizontal plane wall in the upper transition regime
Marine Structures ( IF 3.9 ) Pub Date : 2021-01-01 , DOI: 10.1016/j.marstruc.2020.102872
Marek Jan Janocha , Muk Chen Ong

Abstract Slender subsea structures like pipelines, jumpers and umbilicals when exposed to currents may experience vortex-induced vibrations (VIV), which can shorten their fatigue life and increase the risk of structural failure. In the present study, flow around different configurations of a piggyback pipeline close to a flat seabed has been investigated using the two-dimensional (2D) Unsteady Reynolds-Averaged Navier Stokes (URANS) equations with the k − ω Shear Stress Transport (SST) turbulence model. The Reynolds number (based on the free stream velocity and large cylinder diameter) is equal 3.6 × 106 corresponding to upper-transition regime. The drag forces acting on the cylinders and base pressure coefficient value are well predicted by the present simulations, while the other hydrodynamic quantities (root-mean-square lift coefficient, Strouhal number) are predicted reasonably well as compared to published experimental data. The piggyback pipeline in the present study is modeled as two circular cylinders with a diameter ratio d/D = 0.2 (D denoting diameter of the large cylinder, d is diameter of the small cylinder). These two cylinders are clamped together at a distance G/D = 0.2. The two rigidly coupled cylinders are elastically supported and free to vibrate in two degrees of freedom. The effects on the vibration amplitudes and hydrodynamic forces are analyzed. The flow structures around the cylinders are investigated to explain the variations in observed structural responses. Depending on the angular position (α) of the small cylinder, the lock-in regime is narrower (α = 0°) or significantly wider (α = 180°) when compared to that of a single cylinder.

中文翻译:

上过渡区水平面壁附近背负式管道的涡激振动

摘要 管道、跨接线和脐带缆等细长海底结构在暴露于水流时可能会经历涡激振动 (VIV),这会缩短其疲劳寿命并增加结构失效的风险。在本研究中,使用二维 (2D) 非定常雷诺平均纳维斯托克斯 (URANS) 方程和 k − ω 剪切应力传递 (SST) 研究了靠近平坦海床的背负式管道的不同配置周围的流动湍流模型。雷诺数(基于自由流速度和大圆柱直径)等于 3.6 × 106,对应于上过渡区。目前的模拟很好地预测了作用在气缸上的阻力和基础压力系数值,而其他流体动力学量(均方根升力系数,与已发表的实验数据相比,斯特劳哈尔数预测得相当好。本研究中的背负式管道被建模为直径比 d/D = 0.2 的两个圆柱体(D 表示大圆柱的直径,d 是小圆柱的直径)。这两个气缸以 G/D = 0.2 的距离夹在一起。两个刚性连接的圆柱体由弹性支撑,可以在两个自由度上自由振动。分析了对振幅和水动力的影响。研究了圆柱体周围的流动结构,以解释观察到的结构响应的变化。根据小圆柱的角位置 (α),与单个圆柱相比,锁定范围更窄 (α = 0°) 或显着更宽 (α = 180°)。
更新日期:2021-01-01
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