A Comparative Study of RANS and PANS Turbulence Models for Flow Characterization Around the Joubert BB2 Submarine

This study presents a comparative numerical investigation of Reynolds-averaged Navier–Stokes (RANS) and partially averaged Navier–Stokes (PANS) turbulence models applied to the Joubert BB2 submarine geometry under steady, calm-water conditions. To assess the influence of turbulence resolution and grid density on hydrodynamic performance prediction, simulations were conducted using three mesh resolutions—coarse, medium, and fine—based on unstructured hexahedral grids. The results were validated against international benchmark data, with emphasis placed on total resistance, pressure and shear stress distributions, wake development, and vortex structure. The PANS model consistently outperformed RANS in accurately predicting total resistance and resolving wake asymmetry, especially at medium grid resolution, due to its ability to partially resolve turbulence without full reliance on eddy viscosity assumptions. It demonstrated superior capability in capturing coherent vortex structures and preserving axial momentum in the stern region, resulting in more realistic surface pressure recovery and delayed boundary layer separation. Cross-sectional and circumferential velocity distributions in the propeller plane further highlighted PANS’s enhanced turbulence fidelity, which is essential for downstream propeller performance evaluation. Overall, the findings support the suitability of the PANS model as a practical and computationally efficient alternative to RANS for high-fidelity submarine flow simulations, particularly in wake-sensitive applications where LES remains computationally prohibitive.