单向海流载荷下海底管道局部冲刷试验研究

EXPERIMENTAL STUDY ON LOCAL SCOUR OF SANDY SEABED UNDER SUBMARINE PIPELINE IN UNIDIRECTIONAL CURRENTS

采用量纲分析法建立了海底管道局部冲刷的相似准则,利用模型实验研究了管道局部冲刷的物理过程,以及极限平衡冲刷深度的影响因素。实验观测发现,对于初始嵌入深度较小的管道而言,局部冲刷一般可分为管道悬空、间隙冲刷、尾迹冲刷和平衡冲刷四个特征阶段。在亚临界流动范围内,管道极限平衡冲刷深度与雷诺数的相关性较小。在清水冲刷条件下,无量纲极限平衡冲刷深度随希尔兹数的增加而增大;在所研究的初始间隙比范围内(-0.25<e0/D<0.55),极限平衡冲刷深度与初始间隙比之间大致呈线性递减关系。

The similarity rules for modeling local scour of the under submarine pipeline are established by means of dimensional analytical method. The physical phenomenon of the local scour of the pipeline was modeled in a unidirectional flow flume. The experimental observation indicates that the process of the local scour around the pipeline with an initial embedment mainly includes four characteristic stages： （1） suspension of pipeline, （2） tunnel erosion, （3） lee-wake erosion and （4） equilibrium scouring stages. In the subcritical flow regime, there exists low correlativity between the equilibrium scour depth and Reynolds number. In the case of clear-water scour, the equilibrium scour depth increases with increasing Shields number, and descends linearly with increasing initial gap-diameter ratio in the examined range of initial gap-diameter ratios （-0.25 〈 e0 /D 〈 0.55 ）.