Full-scale ship stern wave with the modelled and resolved turbulence including the hull roughness effect

Stern wave flow phenomena are investigated in a full-scale Kriso container ship. The hull roughness effects are studied with and without propulsion. Reynolds-averaged Navier-Stokes (RANS) and detached eddy simulations (DES) are utilized with the ghost-fluid method (GFM). The DES is carried out with a submodel where a stationary RANS solution is used as a boundary condition. The surface roughness effect on the stern is significant due to the increased boundary layer thickness. The differences in the stern wave shape between RANS and DES become more pronounced with propulsion as DES resolves the turbulence and wave breaking. With the smooth hull, DES indicates transom wetting which RANS does not. For the heavy fouling condition RANS and DES predict a wetted transom. For the smooth hull, the DES results indicate 6.8% higher pressure (2.8% in total) resistance at the transom compared to the corresponding RANS. The resistance of the wetted transom correlates with the velocity change at the transom location. Heavy fouling does not cause pressure resistance although RANS and DES predict a wetted transom. We propose that the increased boundary layer should be taken into account in the after body design.