Analysis On The Influencing Factors Of Underwater Drift Of Group Rock Riprap

Riprap buildings are mostly used in waterway improvement projects,and have the characteristics of simple construction and strong adaptability.During the construction of riprap on the water,the stones will drift under the action of the water flow,and it is not easy to determine the location of the falling points.If the riprap is not in place,it will cause waste of stones and reduced operation efficiency,resulting in loss of resources.Therefore,the construction of riprap buildings can be guided by understanding the interaction mechanism between boulders and the water body,and the law of the falling points’distribution,the drift distance,the diffusion bandwidth,and the variation law of the distribution area.In this thesis,a particle-laden flow model is built by the CFD-DEM coupling solver SediFoam,which is used to couple the computational fluid dynamics program OpenFOAM and the discrete element program LAMMPS.The particle phase equation is the momentum equation which is based on Newton’s second law,the fluid phase equation is the incompressible Navier-Stokes equation,and the flow field is solved by large eddy simulation method.The distribution pattern,average drift distance and distribution area calculated by the numerical calculation of the underwater drift of the stone group are compared with the experimental data of the physical model of the flume,which verifies the rationality of the numerical model in this thesis.The effects of water depth,velocity,turbulence intensity and gradation on the underwater drift of stone are discussed.The study shows that water depth,flow velocity,turbulence intensity and gradation have little influence on the shape of falling point distribution,the increase of particle size will obviously change the shape of falling point distribution,water depth,velocity and turbulence intensity have little influence on the shape of falling points’ distribution.The main influencing factors of drift distance are water depth and velocity.For the same size of block stone group,the water depth is greater,the average drift distance is getting larger,the flow velocity is greater,average drift distance is getting greater.The main factors affecting the diffusion bandwidth and distribution area of block stone groups on the bottom bed are velocity,gradation and turbulence intensity.The velocity is greater,the diffusion bandwidth and distribution area is getting larger,the uniformity and continuity of block stone gradation is getting better,diffusion bandwidth and distribution area of the flow falling on the bottom bed is larger.The turbulence intensity is getting smaller,the diffusion bandwidth and distribution area is smaller.Water depth and vertical distribution of velocity have little effect on diffusion bandwidth and distribution area.