基于CFD-DEM方法对海底管道床面冲刷的研究

采用计算流体力学—离散元耦合方法（CFD-DEM）模拟海底管道床面的冲刷过程。经过模型验证，该方法的计算结果与前人的研究具有较好的一致性，证明其可以应用于海底管道周围的冲刷模拟计算。冲刷初期的结果增强了目前对启动阶段粒子运动机理的理解，即管前后压力梯度造成的渗流作用导致粒子运动。对完整冲刷过程的模拟中，发现冲刷分为冲刷启动阶段、间隙冲刷阶段和尾迹冲刷阶段。间隙冲刷阶段管道下方粒子具有较大速度，冲刷坑快速向下方发展。进入尾迹冲刷阶段后，管道后方出现周期性脱落的涡旋，沙丘上的粒子速度更大。同时利用DEM更具直观性的独特优势，首次得到了14个典型位置处颗粒的运动轨迹和运动速度，对于理解冲刷过程中粒子的运动情况具有较大帮助。

Study of subsea pipeline bed scouring based on CFD-DEM method

A coupled computational fluid dynamics-discrete element method (CFD-DEM) is used to simulate the scouring process at the bed surface of the submarine pipeline. After model validation, the computational results of the method are in good agreement with previous studies, proving that it can be applied to the simulation calculation of scour around the submarine pipeline. The results at the early stage of scouring enhance the current understanding of the mechanism of particle motion during the initiation phase, i.e., the seepage effect caused by the pressure gradient in front of and behind the pipe leads to particle motion. In the simulation of the complete scour process, it is found that scour is divided into scour initiation phase, gap scour phase and wake scour phase. In the interstitial scouring stage, the particles below the pipe have a large velocity and the scouring pit develops rapidly downward. After entering the trailing flush phase, periodic shedding vortices appear behind the pipe and the particles on the dune have a greater velocity. At the same time, using the unique advantage of more intuitive DEM, the trajectory and velocity of particles at 14 typical locations are obtained for the first time, which is more helpful for understanding the movement of particles during the scouring process.