A novel approach for efficient ship hydrodynamic simulations with realistic coastal bathymetries

Accurate numerical prediction of ship motions and hydrodynamic loads is crucial for the design of energy-efficient and reliable vessels. However, the high computational cost of existing high-fidelity numerical models limits their practical use, particularly for simulations involving large domains, complex bathymetries, and long-duration realistic sea conditions. This paper presents a novel and highly efficient numerical model for ship hydrodynamic simulations in realistic sea conditions with a non-hydrostatic three-dimensional solver, initially developed for phase-resolved wave propagation for large nearshore and coastal areas. The model is enhanced with the implementation of a direct forcing immersed boundary method (DF-IBM) by adding a forcing term to the governing equations for six-degree-of-freedom (6DOF) wave–structure interaction simulations. The model predicts the motion responses of floating bodies in waves with accuracy comparable to two-phase flow CFD methods while significantly reducing computational cost. The accuracy evaluation focuses on wave actions and responses, not viscous effects, which require much finer resolution near the structure and are out of the scope of the presented study. The model is tested and validated for wave–structure interaction and ship hydrodynamic cases. Additionally, it is applied to a full-scale ship model under short-crested multidirectional irregular waves in a realistic bathymetry around a Norwegian harbor.