The transient prediction of a pre-swirl stator pump-jet propulsor and a comparative study of hybrid RANS/LES simulations on the wake vortices

The objective of this work is to investigate the transient flow around a pre-swirl stator pump-jet propulsor. Based on the discussion of the unsteady analysis, we conduct a comparative study on the wake vortices generated by the hybrid RANS/LES family at the design operating condition J=1.0. Due to the interaction between the rotor and stator, the rotor working behind the stator causes the fluctuant thrust. However, due to the oncoming flow of the rotor is improved by the pre-swirl effect of the stator, the thrust and pressure fluctuations on the blade surface are low-intensity. Though the shrunk effect of the duct has significantly restricted the tip vortices development, there also exits typical vortices in the wake. The tip vortices induce the shear layer of the duct and then form the second vortices merging into the tip vortices generated by the next blade. The hybrid RANS/LES category catches enough and rich turbulence structures. As they show improved abilities in resolving the vortices in the rotor wake where it is vital for the duct, there are apparent differences in PJP hydrodynamic performance. The IDDES, SDES, and SBES show the prominent resolving ability in vortices motion and evolution than the SAS and DDES.