Assessment of turbulence models for the prediction of Bénard-Von Kármán vortex shedding behind a truncated hydrofoil in cavitation conditions

Abstract

The transient cavitating flow in the wake of a hydrofoil at zero incidence angle has been simulated using a homogeneous mixture cavitation mass transfer model combined with both Reynolds Average Navier-Stokes (RANS) and Scale Resolving Simulation (SRS) turbulence models. The hydrofoil geometry corresponds to a 2D NACA 0009 with a truncated trailing edge which has already been extensively investigated in the High-Speed Cavitation Tunnel of the EPFL. The hydrodynamic conditions of interest correspond to a free stream velocity of 20 m/s (Re = 2 • 106) without cavitation and with two different degrees of cavitation. To improve the prediction of the vortex shedding behing the hydrofoil, the γ - Rθt transitional boundary layer model has been coupled with the turbulence models. At cavitation-free regime, all the turbulence models with the exception of the SST and LES WALE ones have the ability to predict the experimentally measured vortex shedding frequency. Nevertheless, the results indicate that, neither the SST nor the DES-SST γ - Rθt, can predict the vortex shedding frequency increase which has been experimentally observed when cavitation occurs. In contrast, the numerical results provided by the SST γ - Rθt and the SSTCC γ - Rθt show the capability to predict the expected shedding frequencies for both non cavitation and cavitation conditions. Beyond all expectation, the results provided by the LES WALE seem not only to overestimate the vortex shedding frequency at cavitation free conditions but also to underestimate the frequency when the cavitation number is significantly reduced.