Effects of Reynolds number on flow structures and broadband forces of a pump-jet propulsor under non-uniform inflow

Abstract

Under non-uniform wake conditions, the effects of Reynolds-number variation on the broadband-force response of a pump-jet propulsor remain unclear. In this study, an experimentally validated large-eddy simulation method is used to systematically examine Reynolds-number effects on the upstream wake structure, internal flow-field evolution, and spectral characteristics of rotor broadband forces. These results show that increasing Reynolds number leads to a marked contraction of the aft-body boundary layer and the low-speed wake upstream of the propulsor. At the higher Reynolds number, flow separation and wake diffusion in the stator region are suppressed, while rotor–stator shear interaction and local turbulence intensity near the rotor inlet are enhanced. Meanwhile, velocity fluctuations upstream of the rotor are attenuated, reducing the amplitudes of blade lift fluctuations. Flow separation over the rotor blade surface is weakened, and the regions of elevated skin-friction coefficient and pressure fluctuations from the aft half-chord to the trailing edge shrink substantially. These changes significantly reduce broadband fluctuations in the rotor thrust coefficient. The findings provide a physical basis for model-scale testing, numerical prediction, and design optimization of pump-jet propulsors.