NUMERICAL SIMULATION RESEARCH OF SOLID-LIQUID TWO-PHASE FLOW IN VERTICAL PIPE UNDER FORCED VIBRATION

The transportation of coarse-particle solid-liquid two-phase flow in pipes is applicable to deep-sea mining engineering. The transport mechanism of internal solid-liquid two-phase flow in riser pipes under flow-induced vibration has not been fully explored. Therefore, this study employs a coupled computational fluid dynamics (CFD) and discrete element method (DEM) approach to analyze the dynamic characteristics of coarse particles and the variations in the flow field characteristics under forced vibration conditions in pipes with varying particle sizes, different vibration frequencies and amplitudes, and different concentrations. In this analysis, the pipe vibration is simplified as one-dimensional radial vibration, and flexible pipes in practical situations are assumed to be rigid pipes. Research indicates that during pipe vibration, larger particles exhibit greater inertia compared to smaller ones, and the fluid must attain higher velocity to generate increased drag force necessary for propelling these larger particles, resulting in higher axial flow field velocity and greater axial particle velocity. As the particle size increases, larger particles induce more significant perturbations in the flow field, leading to increased forces between the fluid and the pipe wall; additionally, larger particles experience more substantial collisions and frictional forces with the pipe wall, thus amplifying wall shear stress. Simultaneously, the energy dissipated due to frictional losses between larger particles and the fluid is also greater. Consequently, a higher energy input is required to transport these particles, leading to an increase in pressure drop within the vibrating pipe. Increasing the pipe vibration frequency and amplitude leads to a more dispersed particle distribution across the cross-section and greater disturbance to the flow field, albeit with a relatively minor impact on axial flow field velocity. Higher feed concentrations result in more frequent interactions between particles and between particles and the flow field, causing changes in particle distribution and leading to increased axial flow velocity and turbulence kinetic energy.