Investigation on cavitating turbulent flow for the twisted NACA66 hydrofoil using a PANS model with helicity modification

In the present paper, the unsteady cavitating turbulent flow over the twisted NACA66 hydrofoil is investigated based on an modified shear stress transfer k - ω partially averaged Navier-Stokes (MSST PANS) model, i.e., new MSST PANS (NMSST PANS) model, where the production term of kinetic energy in the turbulence model is modified with helicity. Compared with the experimental data, cavitation evolution and its characteristic frequency are satisfactorily predicted by the proposed NMSST PANS model. It is revealed that the interaction among the main flow, the reentrant jets, and sheet cavitation causes the formation of the primary shedding cavity near the mid-span and the secondary shedding cavity at each side of the twisted hydrofoil, and further induces the remarkable pressure gradient around shedding cavities. Along with the development of the primary and the secondary shedding cavities, the great pressure gradient associated with large cavity volume variation promotes the vortical flow generation and the spatial deformation of vortex structure during cavitation evolution, and results in the primary and the secondary U-type vortices. Further, dynamic mode decomposition (DMD) analysis is utilized to confirm the interaction among the main flow, the main reentrant jet and two side reentrant jets, and cavitation. These results indicate that the proposed NMSST PANS model is suitable to simulate the complicated cavitating turbulent flow for various engineering applications.