海底管线作用下沙质海床冲刷深度的计算

Calculation of scour depth for submarine pipeline on sandy seabed

针对海底管线在输送石油过程中出现的管线冲刷问题,采用物理模型试验并控制一系列不同的试验变量,研究了单向恒定流作用下,海底管线未安装阻流器、安装阻流器及不同间隙比作用下,其下方海床冲刷深度的变化规律。试验结果显示,冲刷深度随雷诺数及阻流器高度的增加而增加;冲刷深度随间隙比的增大而减小,同时根据海床冲刷停止的流速公式(冲止流速),认为动水休止角是冲止流速的主要影响参数。利用流体的连续性条件,从不同角度推导了管线安装阻流器且有间隙比条件下冲刷坑深度的计算公式。结果表明:冲止流速、管线周围流场分布是冲刷深度的决定因素。经试验数据与计算公式的对比验证发现,计算值与试验值吻合良好,本文建立的公式能反应冲刷坑深度的变化规律,在实际工程应用中可适当参考此公式。

Aiming at the pipeline scour appearing during oil transportation,a physical model was adopted in experiments and a series of different test variables was controlled. Changes in the depth of scour hole underneath the pipeline were studied under the action of unidirectional steady flow and the following conditions： installing spoiler,not installing spoiler,and different gap ratio. Results demonstrated that the scour depth of the underneath seabed increased with the increase in Reynolds number and spoiler height but decreased following the rise in the gap ratio. In accordance with the formula of erosion-stopping flowing velocity,the repose angle of flowing water was the main parameter influencing the erosion-stopping flowing velocity. By utilizing the condition of fluid continuity,a calculation formula on the depth of the scour hole was deduced from different viewpoints and under the following conditions：the pipeline was installed with spoiler under a gap ratio. The erosion-stopping flowing velocity and the distribution of flow field around the pipeline were the decisive factors of scour depth. By comparing the calculation results with the experimental data,the calculation values and test values coincided well. Therefore,the formula could reflect the changes in the depth of the scour hole,and the formula can be properly referred to in actual engineering applications.