Correlation study of vortices and pressure pulsations in multistage centrifugal pump as turbine

Multistage centrifugal pumps operating as turbines (PATs) are important devices for hydraulic energy recovery. However, vortex-induced flow instabilities cause pressure pulsations and efficiency losses, especially in configurations with complex interstage interactions. In offshore oil and gas field systems—such as platform seawater systems, produced-water treatment systems, and subsea energy recovery—stable PAT operation is essential for reliability and continuous energy utilization. This study investigates the correlation between vortex evolution and pressure pulsation across different stages of a multistage PAT. Numerical simulations and Pearson correlation analysis reveal that in the first three stages, vorticity and pressure pulsation distributions exhibit strong spatial consistency. From the second to the last stage, both vorticity intensity and pressure pulsation amplitude increase markedly compared with the first stage. The first stage maintains a stable flow with weak dynamic–static effects, while downstream stages show less stability, dominated by dynamic interactions. In high-vorticity regions, vortex evolution is the primary cause of pressure fluctuation, and its correlation with pulsation intensity is strongest. In later stages, the vortex–pressure correlation weakens as complex interstage dynamics prevail. Overall, the results confirm a positive correlation between vorticity and pressure pulsation intensity at various locations within the multistage PAT. These findings provide theoretical insight and practical guidance for optimizing impeller–diffuser matching and stage configuration, enabling improved hydraulic stability and enhanced energy recovery efficiency, particularly under offshore and subsea operating conditions.