Abstract: This study examines how trim and draft variations affect the resistance of a full-scale KRISO Container Ship model, considering marine biofouling as a critical contributor to increased hull roughness. Marine biofouling is defined as the growth and accumulation of marine microorganisms on surfaces submerged in aquatic environments. To conduct this study, seven trim configurations, three drafts, and three levels of hull roughness due to biofouling were evaluated using computational fluid dynamics with an open-source Reynolds-averaged Navier-Stokes solver, resulting in sixty-three different combinations. The objective was to quantify how each of these parameters affects the ship's hydrodynamic performance in terms of frictional resistance at a constant speed under calm water conditions. To achieve this, the integrated rough wall function model of OpenFOAM was employed, which accurately characterized the model's roughness without meshing biofouling geometrically. Variations in trim and draft altered the pressure distribution, directly impacting frictional resistance and, consequently, fuel consumption and carbon emissions. A well-optimized trim configuration for the design draft reduced the model's total resistance by 3.94 % in a smooth hull condition and by 1.13 % in a rough hull condition after 24 months of exposure in a real marine environment, emphasizing the importance of proper load distribution on board.
