应用切割单元法对海底管道局部冲刷数值模拟

采用SIMPLEC算法的有限体积法,求解非定常流动的N-S方程,采用k-ω紊流模型,通过模拟均匀无粘性推移质的冲刷和淤积,得到海底管道由搁置在海床上的状态变为悬跨状态这一过程的管道周围局部海床冲刷情况,建立了海底管道局部冲刷的二维数值模型。海底管道从搁置在底床上到冲刷悬空的过程中,管道周围的空间产生了拓扑变化,这给采用贴体网格并在计算过程中进行网格重构的传统方法带来了很大困难,而采用切割单元法,把物体轮廓从静止的背景直角坐标结构化网格中切割出去,计算过程中不需要传统意义的网格重构过程。数值模型预测的海底管道周围局部冲刷结果与Mao的物理模型实验实测结果及Liang和Cheng等的数值模拟结果符合较好,验证了模型的准确性。

Numerical simulation of local scour under a submarine pipeline using a Cartesian cut cell approach

By using finite volume method with SIMPLEC algorithm,the unsteady Navier-Stokes equations combined with k-ω turbulence model are solved.By simulating the scour and deposit process of uniformly noncohesive sediment,the scour process from sitting-on-bed-pipeline status to suspended-pipeline status is simulated and a two-dimensional numerical model for local scour under a submarine pipeline is established.When a submarine pipeline originally placed on the seabed becomes suspended due to local scour,the topography of the space around the pipeline totally changes,thus making the utilization of body-fitted grid combined with re-meshing in the computation extremely difficult.While in this paper,a cut cell approach is used,the outlines of bodies are cut out from a static Cartesian background mesh,and no conventional re-meshing is needed in the computation.The present model is validated by comparing with Mao’s experiment of local scour under a submarine pipeline and Liang and Cheng’s numerical model.The predicted scour process agrees well with the experimental results of Mao and the numerical results of Liang and Cheng.