Flow instability and vortex evolution in a three-twisted-blade pump using delayed detached eddy simulation

The study investigates the fluid dynamics and instability mechanisms of a three-twisted-blade pump using hydrodynamic field analysis, vortex identification, and spectral methods. High-fidelity numerical modeling was conducted with OpenFOAM, employing the Delayed Detached Eddy Simulation method and an arbitrary mesh interface on structured grids. The results identify two distinct fluid motion mechanisms: in the flow passage range of R45%–R60%, significant velocity fluctuations and vortex shedding lead to turbulent flow, while in the R80%–R90% range, the flow becomes more stable with weaker fluctuations. Vortex motion in the flow passages, driven by the twisted blade shape, resembles the Kármán vortex street. On the suction side of the blade leading edge, striped vorticity patterns extend and densify with increased flow rate and rotational speed, correlating with the vortex shedding frequency. An increased flow rate promotes the transition from single-axis to multi-axis frequency in the velocity Power Spectral Density (PSD), counteracting the volute tongue effect and eliminating single-blade frequency. Conversely, higher rotational speeds intensify turbulence near the blade tip but minimally affect the velocity PSD's peak frequency domain.