CHARACTERISTICS OF A SPHERICAL PARTICLE MOTION IN AN OSCILLATING RISER WITH UPWARD FLOW

In deep-sea mining, vibrations can be induced when the lifting risers subject to ocean waves and currents, and these vibrations have an impact on the lifting efficiency and ores motion transported inside the risers. Here, by using the governing equation for motion of a spherical particle and the soft sphere collision model, the particle movement in a riser with upward flow and oscillating in the lateral direction is investigated. Validations are conducted based on comparisons of our data with numerical and experimental results. Then, the motion of a single particle in the vibrating riser is explored, considering the effects of the frequency and amplitude of the riser vibrations, the density ratio of the particle to the fluid, and the diameter ratio of the particle to the riser. It is found that the average of the vertical velocity of the particle decreases with the vibrational frequency and amplitude of the riser, density ratio and diameter ratio increasing. In addition, without the occurrence of collision between the particle and riser wall, as the vibrational frequency and amplitude, density ratio and diameter ratio increase, the amplitude of relative lateral velocity between the particle and riser in the vibrational direction, the phase difference between the particle velocity and riser velocity as well as the fluctuation amplitude of the vertical velocity shows an increasing trend. Compared to the absence of collisions, a sharp increase in the fluctuation amplitude of the particle vertical velocity can be caused by the collision between the particle and riser wall. In addition, an increase of the density and diameter ratios can lead to the early appearance of collision between the particle and the riser wall, making collisions more likely to occur, while the effects of the density ratio and diameter ratio on the lateral velocity and vertical velocity can be decreased.