Experimental and Numerical Investigation on the Transport Characteristics of Particle-Fluid Mixture in Y-Shaped Elbow

The Y-shaped elbow is used as a connecting pipe between the buffer and the lift pipe in the deep-sea mining system. After being mixed with seawater in the Y-shaped elbow, nodule particles are lifted to the sea surface mining ship via the lift pump. In this paper, we employ a computational fluid dynamics and discrete element coupled method (CFD-DEM) to study the characteristics of particle transport in the Y-shaped elbow. Considering a large diameter of the particles, we discuss the behavior of particles and fluid under different conveying velocities. In addition, the simulation was verified based on the experiment. The results show that the simulation agrees well with the experiment. On this basis, the distribution and motion characteristics of the particles in the Y-shaped elbow were obtained. The interaction between fluid and particles is also discussed. These findings suggest that the particles can be successfully transported when the pump runs at medium to high frequencies. The particles are basically moving along the pipe wall and slower than the fluid flow. Moreover, it was found that the particle motions are more complex with the increasing of conveying velocities, and it is closely related to the secondary flow of fluid. Some suggestions on the actual particle transportation can be put forward based on the research in this paper.