Analysis on unsteady flow dynamics in a slurry pump based on refinement dynamic mode decomposition

The stable operation of slurry pumps is critical to ensuring the safety and reliability of deep-sea mining systems. However, the internal flow field within these pumps exhibits complex unsteady behaviours that pose significant challenges to performance optimisation. To investigate the unsteady flow characteristics, this study applies the Singular Value Energy-based Truncation Dynamic Mode Decomposition (SVET-DMD) method to extract and analyse the dominant modes in each stage of the flow passage components. The results indicate that the SVET-DMD method markedly enhances both the overall reconstruction accuracy and the fidelity of dominant mode reconstruction. Quantitative analysis demonstrates that the SVET-DMD method reduces the full-field reconstruction error from 13.22% to 0.66%, ensuring accurate reconstruction of the overall flow field, while lowering the dominant mode error by 6.89% compared with the uncorrected result, thereby enhancing the fidelity of dominant flow structures. Flow structure analysis reveals that the vortex formation on the pressure side of the first-stage impeller is induced by alternating positive and negative pressures at the guide vane frequency. In contrast, a transitional zone forms in the impeller, which suppresses vortex development. Vortex formation on the suction side of the guide vane is dominated by low-frequency modes, with positive and negative pressures persisting over time. Vortices are generated under the influence of pressure gradients. Finally, based on the mechanisms of vortex formation, optimisation strategies are proposed to suppress vortex structures.