A discrete-forcing immersed boundary method for turbulent-flow simulations

For numerical simulations of ship hydrodynamics in high Reynolds number, near-wall grids with high quality are essential to accurately predict the flow field and shear stress. This article proposes a discrete-forcing immersed boundary method to simulate moving solid boundaries in turbulent flows. The technique will efficiently remove the requirement of high-quality body-conforming grids and also preserve the grid quality throughout the simulation when body motions are considered. The one-equation Spalart-Allmaras turbulence model is coupled with the immersed boundary method for turbulence closure. A key aspect of this method is to use a wall function to alleviate the near-wall cell-size requirement in high-Reynolds-number flows. In this method, the boundary conditions on the immersed surfaces are enforced without the need of spreading functions, which is favorable for high-Reynolds-number flows. The performance of the method is carefully verified and validated through various problems, including both laminar and turbulent flows for fixed and moving solid surfaces. Subsequently, this method is further examined by predicting the turbulent flows around a model-scaled double-body KVLCC2 tanker. The total resistance and the local wake field are compared with experimental data.