稳定流作用下的二维海底管道底部冲刷数值分析

Numerical Analysis of 2-D Submarine Pipeline Scour Under Steady Current

针对目前海底管道底部冲刷研究的不足,选取RNG k-ε湍流模型求解管道周围流场,采用Tru-VOF法追踪水-沙界面,建立了稳定流作用下的二维海底管道底部冲刷数值模型。后续选择经典管道冲刷物理实验数据验证了该模型具有较高的精度及可靠性,并运用此模型详细分析了海底管道底部冲刷坑的形成和发展机理。同时,进一步探讨了入流流速、静水深度、管道直径以及管道与沙床间隙等相关参数对冲刷坑发展的影响。结果表明:水流入流流速越小,静水深度越大;水深与管径比越大(一般在3.5≤h/D≤7内),管道与沙床间隙越大;均会造成分流后管道下方水流流速减小,沙床表面瞬时剪切应力变小,输运泥沙能力减弱,进而使得冲刷坑所能达到的平衡冲刷深度越小。

Aiming at enriching the current studies of the submarine pipeline scour,a two-dimension numerical model is proposed to study the bottom scour of a single submarine pipeline under steady current.The RNG k-εturbulence model was used to solve the flow field around the pipeline,and the Tru-VOF method was chosen to track the water-sand interface.In order to validate the accuracy and applicability of the model,numerical investigation of the classical physical experimental date of pipeline scour is conducted.Then,the model was employed to simulate the generation and development of submarine pipeline bottom scour pit,and the related underlying mechanism was described in detail.In addition,the effects of current flow velocity,hydrostatic depth,pipeline diameter,and the gap between pipeline and sand bed on the development of scour pit were systematically investigated.It is found that the smaller current flow velocity,the larger hydrostatic depth,the larger ratio of hydrostatic depth to pipeline diameter(generally in 3.5≤h/D≤7),and the larger gap between the pipeline and the sand bed,will all cause the decrease of the flow velocity at the bottom of the pipeline after shunting.Meanwhile,the shear stress of sand bed becomes smaller and the transport capacity of sediment is weakened,which results in a smaller equilibrium scouring depth for the scour pit.