Unsteady flow structures and noise characterization under stator skew in pump-jet propulsors

This study explores how stator skew affects pump-jet propulsor (PJP) performance. A hybrid Reynolds-averaged Navier-Stokes/large eddy simulation strategy is utilized to analyze the flow, and the Ffowcs Williams-Hawkings equation is applied for noise calculation. First, the original PJP is examined and found that the stator's trailing edge vortex strongly affects the flow field's fluctuation. Next, different stator skews are examined, and it is observed that skew increases the flow speed around the blades, particularly the circumferential speed. This results in a larger rotor incidence angle and stronger fluctuations. It is also found that high skew generates strong vortices at the stator corner, which disrupt the rotor blade tip vortex and amplify flow field fluctuations. Finally, the impact of skew on noise is studied. Low skew is shown to reduce noise levels while discrete frequency features are maintained. High skew is associated with increased overall noise levels, especially broadband noise. In general, noise levels are found to rise as skew increases. This research provides a new method for reducing noise in PJPs.