The momentum flow exchange between the impeller and side channel produces highly turbulent flows in side channel pumps. The turbulent flows feature complex patterns of vortex structures that are partly responsible for the dissipation of energy losses and unsteady pressure pulsations. The concept of turbulent flows in side channel pumps requires a reliable vortex identification criterion to capture and predict the effects of the vortex structures on the performance. For this reason, the current study presents the application of the new Ω -criterion to a side channel pump model in comparison with other traditional methods such as Q and λ ₂ criteria. The 3D flow fields of the pump were obtained through unsteady Reynolds-averaged Navier-Stokes (RANS) simulations. Comparative studies showed that the Ω -criterion identifies the vortex of different intensities with a standard threshold, Ω =0.52. The Q and λ ₂ criteria required different thresholds to capture vortex of different intensities thus leads to subjective errors. Comparing the Ω -criterion intensity on different planes with the entropy losses and pressure pulsation, the longitudinal vortex plays an important role in the momentum exchange development which increases the head performance of the pump. However, the rate of exchange is impeded by the axial and radial vortices restricted in the impeller. Therefore, the impeller generates the highest entropy loss and pressure pulsation intensities which lower the output efficiency. Finally, the findings provide a fundamental background to the morphology of the vortex structures in the turbulent flows which can be dependent upon for efficiency improvement of side channel pumps.

Large high-head centrifugal pumps have the characteristics of large flow rate, high head, and high specific speed, making them important engineering equipment in large-scale water transfer projects. However, these pumps inevitably cause the death of a large number of fish during operation, which has adverse effects on the ecological environment. Therefore, studying the damage of large high-head centrifugal pump stations on fish is of great significance. This article establishes a new mathematical model for blade strike and predicts the strike probability and mortality rate of fish passing through the inlet of the centrifugal pump impeller. The prediction results show that under various flow conditions, the strike mortality rate for 50 mm fish passing through the model pump exceeds 82.5%, indicating that the model pump will cause significant damage to the pumped fish. This article further investigates the damage to fish caused by unstable flow inside the impeller and diffuser in low-pressure, high-shear, and high-pressure gradient regions. The research results show that fish suffer less low-pressure damage and more high-pressure gradient damage while passing through the model pump.