Forces On Sediment Particles Under Different Exposure Degree

It is the foundation and key point for ones who study on a swarm of sediment particles movement and participate in practical engineering to fully understand the transport mechanics of a single sediment particle.The most natural particles are not uniform and they move randomly,what's more,the flow field is stochastic.All this makes it difficult to get the forces acting on particles.The forces acting on a particle include the gravity,interaction force between particles,drag force and lift force induced by the fluid force,and friction after moving.The analysis of all these forces is complex because it is affected by so many factors such as fluid field conditions,particle shape,surface roughness,fluid concentration,grain composition,particles arrangement,sediment exposure degree and so on.In a very long time,the effect of forces on particles have received considerable attention at home and abroad on sediment entrainment research,and scientists have made great progresses.But we still have a long way to study well the non-uniformed particles in turbulent flow with a great Reynolds number.This paper focuses on the numerical simulation by Flow3 D of the forces on sediment particle in steady turbulent flow.For single particle,the paper focuses on the velocity gradient,and for the particle group,it is the exposure degree of different arrangement.The paper gives experimental relations of the drag and lift coefficients with different particle diameters,exposure degree and velocities.And what's more,the streamlines near the particles is given by the means of Tecplot360.In its opinion,vortex exists in three dimensions,and the streamlines behind particles interweave like twisted lines which makes the vortex cannot be closed within any plane.