往复流作用下海底管道局部冲刷机制数值模拟

基于开源的计算流体力学模式REEF3D，建立了海底管道局部冲刷水槽数值模型，在验证单向流实验结果的基础上，进一步对往复流作用下的海底管道局部冲刷机制进行了研究，并作对比分析。研究表明，总体上，往复流对管道所在海床局部冲刷规模比单向流弱。当流向改变后，原先下游的堆积区转变成上游，优先受到冲刷，并填充到管道下方的冲刷坑，同时使水流在管道下方的作用减弱。这种回填过程，使短周期下的往复流作用需要更长的冲淤平衡时间。在这种回填与冲刷的共同作用下，上下游的冲刷坑坡度会因流向变化而变化。

Numerical simulation of local scour of submarine pipeline under reciprocating flow

By using the open source computational fluid dynamics software REEF3D, a numerical model of submarine pipeline local scour is established. This paper studies the development process of local scour of submarine pipeline under the condition of bidirectional flow, and a comparison is made with the unidirectional flow. It is found that the bidirectional flow is weaker than the unidirectional constant flow in local scour scale. The reason is that the deposit on downstream of the scour pit is washed into the scour pit firstly after the change of flow direction, which weakens the effect of water flow under the pipeline. This phenomenon is called backfill. Backfill makes the sediment scour reach the balance of scour and deposition in bidirectional flow for a longer time. Under the combined action of backfill and scour, the slope of scour pit in upstream and downstream will change with the change of flow direction.