Study of sedimentation of non-cohesive particles via CFD–DEM simulations

Abstract

The sedimentation process of granular materials exists ubiquitously in nature and many fields which involve the solid-liquid separation. This paper employs the coupled computational fluid dynamics and discrete element method (CFD-DEM) to investigate the sedimentation process of non-cohesive particles, including the hindered settling stage and the deposition stage. Firstly, the coupled CFD-DEM model for sedimentation is validated by the hindered settling velocity at different solid volume concentrations of suspension , i.e., = 0.05~0.6. Two typical modes of sedimentation are also presented by the concentration profiles and the equal-concentration lines. Then, the comparisons between mono-and poly-dispersed particle system are detailed. In the sedimentation of the poly-dispersed particle system, the segregation phenomenon is simulated. Furthermore, this segregation effect reduces with the increase of the initial solid concentration of suspension. From the simulations, the contact force between every pair of particles can be obtained, hence we demonstrate the "effective stress principle" from the view of the particle contact force by giving the correspondence between the particle contact force and the "effective stress", which is a critical concept of soil mechanics. We also demonstrate the effective stress principle from the view of the contact force acting on particles.Moreover, the deposition stage can be simulated by CFD-DEM method, therefore the solid concentrations of sediment bed max on different conditions are studied. Based on the simulation results of max and the theory of sedimentation, this paper also discusses a method to calculate the critical time when sedimentation ends of two typical modes of sedimentation.

Investigating the jamming of particles in a three-dimensional fluid-driven flow via coupled CFD–DEM simulations

“…This solver was developed by Xiao and Sun (2011) based on two open-source codes: (a) the CFD toolbox OpenFOAM (OpenCFD, 2013) and (b) the molecular dynamics simulator LAMMPS (Plimpton, 1995). SediFoam has been demonstrated to be a capable tool in simulating many particle flow problems, e.g., a fluidized bed (Xiao and Sun, 2011;Gupta, 2015), sediment transport (Sun and Xiao, 2016), and sedimentation (Xu et al, 2018;Sun et al, 2018), etc. In these areas, the mathematical models mentioned above for the particle motion, fluid flow, and the interaction force have been verified and extensively validated.…”

“…The value of the inter-particle contact force is larger in the higher-speed flow, represented by the larger-diameter cylinder with the darker colour. Moreover, we calculate the value of averaged contact stress σ con on the y-z planes proposed by Xu et al (2018), which increases obviously with the fluid velocity, as shown in Fig. 19.…”

A Coupled CFD–DEM Simulation of Slurry Infiltration and Filter Cake Formation during Slurry Shield Tunneling

“…The lift force, including Saffman lift forces and Magnus lift forces, accounts for the lift or upward force due to particle rotation. In the process of particle sedimentation, particles may fall in the vertical direction with rather little acceleration, in which the effect of lift force and virtual mass force could be neglected [17]. Hence, in the present simulation, only the drag force and pressure gradient force are considered.…”

“…ε −χ+1 in Equation (5) denotes the porosity correction function to consider the presence of other particles in the flow system, as proposed by Di Felice [17]:…”

Packing dynamics of spherical and nonconvex grains sedimenting at low Stokes number

“…In this way, the interparticle collisions play a fundamental role. The dynamics of collective granular packing is addressed in the context of cake formation for spherical particles [21,22]. However, as far as we know, no information is available in case of nonspherical nonconvex grains.…”