Motion of a solid particle in an ore-lifting riser with transverse vibrations

Abstract

Deep-sea mining lifting risers experience vibrations induced by the action of ocean waves and currents, and these vibrations have an impact on the lifting efficiency of ores transported inside the risers. Here, to investigate the effect of riser vibration on ore transport, the motion of a single solid particle in a riser oscillating in the lateral direction is simulated taking account of collisions between the particle and the riser using the governing equation for motion of a spherical particle in Poiseuille flow and the Hertz–Mindlin soft sphere collision model. Validations are conducted based on comparisons between numerical and experimental results. Then, the motion of the particle in the vibrating riser is explored, considering the effects of the initial position of release of the particle, the frequency and amplitude of the riser vibrations, and collisions between the particle and the riser. It is found that the initial position of release affects only the initial motion of the particle, but not its overall motion. With increasing vibrational frequency and amplitude of the riser, the relative lateral velocity of the particle shows an increasing trend, while its vertical velocity and lifting distance are clearly decreased. The frequency with which the vertical particle velocity varies is twice as the vibrational frequency of the riser. Moreover, collisions have significant effects on the particle motion, especially on the velocities of the particle, the phase difference between the displacements of the particle and the vibrating riser, and the particle trajectory. Finally, the behavioral regime map of the particle under different vibrational frequencies and amplitudes of the riser is established preliminarily.