导流板对海底管线防护功能的试验研究

Experimental Study on the Function of Spoilers in Protecting Submarine Pipeline

提出一种防止海底管线冲刷的新方法。海底管线底部安装柔性导流板来改变周边流场及压力分布,减小管线两侧的压力差,达到减小甚至阻止管线冲刷的目的。通过理论分析和物理模型试验对单向流和往复流作用下安装柔性导流板、刚性导流板(spoiler)和无导流板的海底管线表面压力分布、管线两侧的压力差和底部的冲刷进行了比较分析。结果表明刚性导流板使管线两侧的压力差增大,冲刷深度和范围都明显增大,并且使管线受到向下的压力,在砂质海床条件下可以实现管线的自埋。但是对于礁石性海床(礁石对管线形成部分管跨支撑)上铺设的管线容易因部分悬空而发生疲劳破坏。单向柔性导流板使管线两侧的压力差减小,冲刷深度减小,并且使管线受到的升力增大,对保持管线稳定有一定的防护作用;双向柔性导流板对管线防护效果更好,导流板达到一定长度后管线两侧压力差接近于0,管线底部冲刷基本消失,实现了对管线有效的防护。

A new method was proposed to protect submarine pipelines.Flexible spoilers were installed under the submarine pipeline to change the flow field and pressure distribution,and reduce the pressure gradient between both sides of the pipeline,so that to decrease or prevent submarine pipeline being washed out.Pressure on the surface of the pipe,pressure gradient between both sides of the pipeline and scour under the pipelines with flexible spoilers,rigid spoilers and without spoilers were compared under unidirectional current and reversing current.Experiment results indicated that rigid spoilers increase the pressure gradient between both sides of the pipeline,increase the scour depth and range,and make the pipe suffer a down pressure,and therefore make pipelines self-burying under the sandy seabed.However,they are not fit for the rocky seabed because rocky span shoulders support parts of the pipeline and prevent it sinking,fatigue failure is easy to happen due to part of the pipeline impending.leading to the seabed erosion and environmental damage.Flexible spoilers decrease the pressure gradient and the scour depth and increase the lift force so that to keep the pipe stable under unidirectional current.And the protective effects of bidirectional flexible spoilers are better.When the flexible spoilers reach a certain length,the pressure gradient is close to zero and the bottom scour almost disappears.So the effective protection for submarine pipeline can be obtained.