Numerical simulation of hydraulic lifting of multi-sized coarse particles in laterally vibrated pipe for deep-sea mining

In deep-sea mining, the efficient and stable transportation of coarse particles in the vertical riser is a key technical challenge to ensure the safe operation of the system. Based on the coupled method of computational fluid dynamics (CFD) and the discrete element method (DEM), this paper studies the transport behavior of multi-sized coarse particles under transverse vibration conditions and focuses on exploring the effects of the standard deviation of particle size distribution, vibration parameters, and feed concentration on the flow characteristics of solid–liquid two-phase flow. The results show that the pipe vibration induces the periodic transverse migration of particles, and at a specific phase, a near-wall aggregation layer is formed. The disturbed boundary layer structure leads to a directional difference in wall friction. As the standard deviation of the particle size distribution increased from 0 to 0.001, the average axial velocity fluctuation of the particle group was reduced by 35%, improving the stability of the transport system. However, it also leads to an increase in pressure drop and energy consumption. At low amplitudes and frequencies, it is more advantageous to use single-size particles for conveying. At high amplitudes and frequencies, the increased inertial force causes the particle group to gradually aggregate from the center of the pipe toward the wall. In addition, increasing the feeding concentration can enhance the conveying efficiency, but it will also exacerbate the risk of energy loss and equipment wear.