Computational investigation of vortex dynamics in a high-speed multi-stage pump

In the depths of the ocean, where minerals lie buried beneath layers of sediment, multi-stage pumps serve as the workhorses of deep-sea mining, lifting extracted materials through immense vertical distances. To ensure their efficiency and reliability, a comprehensive hydrodynamic analysis is required, focusing on vortex-induced vibrations and fluid–structure interactions. In this study, numerical simulations were conducted using computational fluid dynamics to investigate the internal flow characteristics of a multi-stage deep-sea pump. The distribution and formation mechanisms of vortices were analyzed using the omega vorticity identification method, which allowed for the capture of vortex structures and the evaluation of entropy production in the impeller and guide vanes across varying flow rates. The results revealed that at low flow rates, complex vortex structures, including flow separation and reflux vortices, were predominant at the impeller inlet. As the flow rate increased, these vortices gradually dissipated, leading to a more stable wake at the impeller outlet, while separation and reflux vortices became more pronounced at the guide vanes' inlet and outlet. A reduction in the blade passage vortex structure was also observed with increasing flow rates. Further analysis demonstrated that the stretching and twisting term played a crucial role in the formation, evolution, and dissipation of vortex structures at the guide vanes' inlet. Meanwhile, the Coriolis force was identified as a key factor in vortex generation at the impeller inlet and within the blade passage. These findings provide valuable insights into the vortex dynamics governing deep-sea pump hydraulics, offering a foundation for optimizing their design to enhance operational performance and ensure more efficient deep-sea resource extraction.