波流作用下大直径单桩的局部冲刷特征分析

Local scour of large diameter monopile under combined waves and currents

局部冲刷是水利和海洋工程中常见的现象,波流耦合和桩径效应使得这一问题更加复杂。为了进一步研究波流作用下大直径单桩的局部冲刷特征,在CFD软件FLOW3D中建立波浪水槽的数值模型,并设计物理模型试验,通过对比局部冲刷的时空特征,验证了数值模拟的准确性。基于某海上风电场桩基工程,采用随机波描述波浪运动,大涡模拟计算湍流运动,分析了波流耦合作用下大直径单桩的局部冲刷特征。结果表明:局部冲刷的空间发展可以分为纵向切蚀、横向扩展和基本稳定3个阶段。最大冲刷深度出现在桩前,为4.9m,约为0.9倍的桩径。相对应地,局部冲刷的时间发展同样为3个阶段,即快速增长、缓慢增加和冲淤平衡。在20 h后,最大冲刷深度基本不变,冲刷达到稳定状态。

Local scour often occurs in hydraulic and ocean engineering.Wave-current coupling and pile diameter effect make this problem very complicated.In order to study the local scour characteristics of large diameter monopile under combined waves and currents,a numerical model was established in the CFD software FLOW 3 D,and a physical model test was designed.By comparing the scour depth in the physical model test and the results in numerical simulation,the accuracy of numerical simulation was verified.Based on an offshore wind farm project,a field-scale numerical model of seabed and monopile was established.The waves were described by random theory and the turbulence was calculated by large eddy simulation method,and the local scour characteristics of a large diameter monopile under combined waves and currents were analyzed.The results show that the spatial development of local scour can be divided into three stages:longitudinal cutting,lateral spreading and stabilization.The maximum scour depth was 4.9 m in front of the pile,which was about 0.9 times of the pile diameter.Correspondingly,the time development of the local scour can also be divided into three stages:rapid growth,moderate growth and stabilization.After 20 hours,the maximum scour depth remained unchanged,and the local scour reached a stable state.