CFD-DEM Simulation of Sand-Retention Mechanisms in Slurry Flow

The primary motivation of this paper is to investigate the sand-retention mechanisms that occur at the opening of sand filters. Various retention mechanisms under various conditions are explored that have a particulate flow with a low concentration of sand particles (called slurry flow) such as particle shape, size, and concentration. The computational fluid dynamic (CFD)-discrete element method (DEM) model is applied to predict the retention mechanisms under steady flow conditions of the well-bore. By using coupled CFD-DEM (CFD to model the fluid flow, and DEM to model the particle flow), the physics involved in the retention mechanisms is studied. The coarse grid unresolved and the smoothed unresolved (refined grid unresolved) coupling approaches implemented in STAR-CCM+ (SIEMENS PLM) are used to transfer data between the fluid and solid phases and calculate the forces. The filter slots under investigation have different geometries: straight, keystone, wire-wrapped screen (WWS) and seamed slot and the particles are considered with different shapes and different aspect ratios and size distributions. The flow regime is laminar in all simulations conducted. The CFD-DEM model is validated from the perspectives of particle-fluid, particle-particle, and particle-wall interactions. Verification of the CFD-DEM model is conducted by mesh sensitivity analysis to investigate the coupling resolution between the CFD and DEM. By simulation of numerous slurry flow scenarios, three retention mechanisms including surface deposition, size exclusion, and sequential arching of particles are observed. However, the concentration of particles is too diluted to result in multiparticle arch formation. In the simulations, various conditions are tested to give us an insight into the parameters and conditions that could affect the occurrence of the retention mechanisms. As an example, the importance of the gravity force and interaction forces on retention mechanisms are confirmed at the microscale in comparison with others forces involved in retention mechanisms such as the drag force, lift force, cohesive force, buoyancy force, and virtual mass force.

Automated summary

This paper investigates sand retention mechanisms in sand filters at the opening, exploring various mechanisms under different conditions using a CFD-DEM model. The model is validated and three retention mechanisms are observed through simulations. The importance of gravity and interaction forces at the microscale in relation to other forces involved in retention mechanisms is confirmed.