Resolved CFD-DEM simulations of the hydraulic conveying of coarse grains through a very-narrow elbow

This paper investigates numerically the hydraulic conveying of solids through a 90$^{\circ}$ elbow that changes the flow direction from horizontal to vertical, in the very-narrow case where the ratio of pipe to particle diameters is less than 5. We performed resolved CFD-DEM (computational fluid dynamics - discrete element method) computations, in which we made use of the IB (immersed boundary) method of the open-source code CFDEM. We investigate the effects of the water flow and particle injection rate on the transport rate and sedimentation by tracking the granular structures appearing in the pipe, the motion of individual particles, and the contact network of settled particles. We found the saturated transport rate for each water velocity and that a large number of particles settle in the elbow region for smaller velocities, forming a crystal-like lattice that persists in time, and we propose a procedure to mitigate the problem.