Research On Scour Characteristics Of Pile Foundation Based On CFD-DEM Coupling Simulation

With the development of wind energy and technology,the design of wind turbines tends to be large-scale and has gradually shifted from land to offshore region.However,the working environment of offshore wind turbines and piers are complex and changeable,and they are often subject to the coupling action of turbulence,sediment particles and waves,because the existence of pile foundation will affect the flow pattern and increase the turbulence around the pile foundation.The blocked flow in front of the pile causes horseshoe-shaped vortex wake,which erodes and transports sediment particles from the riverbed and then begins to scour.Once the pile foundation becomes unstable due to scouring,it will cause irreparable losses.Therefore,it is necessary to study the local scouring characteristics around the pile foundation.In this paper,CFD method and DEM method are used to calculate the Flow-Sedimentation coupled simulation model of cylinder based on CFDEM.The flow and sediment scouring characteristics around the cylinder are calculated,and proposed a new type of scour protection measure.Details are as follows:First,using the flow around a cylinder with Reynolds number of 3900 as reference,the density of the grid is verified,the velocity characteristics of the flow field under the hydrodynamic model are studied,and the calculation accuracy of the hydrodynamic model is verified.The hydrodynamic model of baffle and cylinder is studied and the hydrodynamic characteristics of different distances between baffle and cylinder are explored.Second,based on the CFDEM software and modified theory,the numerical simulation is simulated to verifies the accuracy of the Flow-Sedimentation coupled simulation model.The scouring depth around the cylinder in different flow velocities were calculated,and the effects of water flow intensity on local scouring of the cylinder were summarized,which lays a foundation for the research on scour protection measure in the future.Finally,CFDEM software is used to calculate the scour when installing collar and combined protection device around the cylinder.Using collar combined with baffle as the combined protection device.By adjusting the distance between the baffle and cylinder,the simulation of the combined protective device is carried out to assessing the effectiveness of protection.The maximum scouring depth and scouring pit range of cylinder under unidirectional flow were calculated,and the effects of collar and combined protection device on local scouring around the cylinder were studied respectively,with emphasis on the influence of baffle distance on flow field characteristics and sediment scouring characteristics.In this paper,the relevant calculation and result analysis of scour around pile foundation provide a certain theoretical support and reference for designs of scour protection devices in the future.