Scale Effects on Bare-Hull Resistance of KCS and JBC: A RANS-Based Investigation with Verification and Validation

This study investigates the calm-water resistance, flow pattern, pressure distribution including scale effect of two benchmark vessels, the KRISO Container Ship (KCS) and the Japan Bulk Carrier (JBC), using Reynolds-Averaged Navier–Stokes (RANS) based CFD simulations. Both model-scale and full-scale analyses were performed with STAR-CCM+, employing the k-ε and k–ω SST turbulence model and a finite-volume discretization. For the JBC hull, sinkage and trim were computed using the Dynamic Fluid Body Interaction (DFBI) module, while the KCS hull was analyzed at fixed even keel to replicate experimental conditions. Verification and validation were carried out through grid convergence studies and comparison with experimental fluid dynamics (EFD) data, with total resistance coefficient, sinkage, and trim predicted within 5% error. Scale effects were assessed through full-scale simulations, supported by visualizations of flow fields and pressure distributions. The results reveal distinct scale-dependent behaviors between the two hulls: the KCS exhibited an increase in pressure resistance at full scale, while the JBC showed a decrease. This contrasting trend highlights the influence of hull form on pressure–friction balance and underscores the limitations of conventional model-to-full-scale extrapolation. The findings provide further evidence that consistent CFD frameworks can capture hull-form-dependent scale effects and contribute to more reliable performance predictions in ship design.