海底矿石软管中水力输送数值模拟研究

海底矿石在软管中的水力输送是深海采矿的重要过程。采用计算流体动力学—离散元耦合的计算方法（CFD-DEM），对矿石颗粒在软管中的输送进行数值模拟，重点关注矿石颗粒的运动、分布规律以及管壁受到的颗粒作用力，分析输送速度和输送浓度（入射颗粒的体积分数）对输送过程的影响规律，探索管道中易发生堵塞、易受颗粒磨损的区域。结果表明，软管中颗粒的动力学特性与管道倾角、输送速度和输送浓度有关。颗粒主要沿管道截面底部推移，倾角较大的上升段出现处于悬移状态的颗粒；管道横截面内颗粒运动速度从上至下递减，截面中心处颗粒的速度接近输送速度。输送过程中颗粒的局部浓度（该区域颗粒与固液两相流的体积比）始终大于输送浓度，局部平均速度始终小于输送速度。上升段颗粒体积分数大于下降段，颗粒速度小于下降段。管道拱顶和谷底位置管壁所受颗粒作用力最明显，管壁最可能受颗粒磨损。

Numerical study on hydraulic transportation of seabed ores through a hose

The hydraulic transportation of seabed ores through a hose is an important process in deep-sea mining. In this paper, the coupled simulation of computational fluid dynamics and discrete element method is adapted to study the hydraulic transportation of ore particles through a hose. The motion and distribution of ore particles, and the contact forces on pipe wall are mainly focused on. The influences of the conveying speed and the conveying concentration (the volume fraction of incident particles) on hydraulic transportation are analyzed to explore the positions that are prone to blockages and wear. The results show that the particle motion is related to the inclination of pipe, the conveying speed and concentration. The particles mainly move along the bottom of the pipe cross-section. However, some particles in suspended state appear in the ascending segment with a large inclination angle. The velocity of the particles decreases from top to bottom within the cross-section, and it is close to the conveying speed in the center of cross-section. The local average concentration (the volume ratio of particles to solid-liquid two-phase flow in this area) of the particles is always larger than the conveying concentration, and the local average velocity is always smaller than the conveying speed throughout the transportation process. The volume fraction of the particles in the ascending segment is larger than that in the descending segment, and the local average velocity of the particles in the ascending segment is smaller than that in the descending segment. The contact force on pipe wall is greater at the dome and the trough of the pipe which are prone to wear by particles.