Effect of cross-flow on vertical and inclined tailwater discharge in deep-sea mining

Seafloor mineral resources are rich in various energy metals and are crucial in advancing industrial development. However, the particle plumes generated by tailwater discharge during deep-sea mining significantly impact the marine environment. This study investigates the flow dynamics and particle sedimentation of tailwater discharge under cross-flow conditions in model scale. Numerical simulations are conducted by using the Eulerian–Eulerian multiphase model. After convergent studies and validation by comparison against the available experimental data, extensive numerical studies are conducted to evaluate the effects of cross-flow velocity and discharge angle on flow evolution. The results show that both cross-flow and inclined discharge alter the plume dynamics, with cross-flow having a more pronounced impact. Cross-flow dominates the flow evolution and reconfigures the plume structures. It accelerates the plume and shifts the particle distribution laterally, forming a horseshoe-shaped pattern. Low-speed cross-flow bends the plume downstream, while high-speed flow leads to bifurcation. Inclined discharge leads to localized changes in flow patterns, causing the plume to bend downward due to negative buoyancy and forming an elongated sediment ring with a wider spreading range on the downhill side. These findings provide a scientific foundation for engineering solutions to mitigate environmental impacts of tailwater discharge in deep-sea mining.