In this research, the vertical bending moment in the mid-ship when a ship encounters nonlinear waves is investigated. To calculate the nonlinear structural response, a 3D Computational Fluid Dynamics (CFD) simulation of the ship, based on the Smoothed Particle Hydrodynamics (SPH) method, is conducted. Two SPH models, based on two different boundary conditions, the Dummy Particle Condition (DPC) and the Dynamic Boundary Condition (DBC), are generated. The influence of the boundary condition on the vertical bending moment of the ship is demonstrated by comparing it with the model test data. It is clarified that the model based on DPC shows better consistency with the model test data.
To achieve higher economic efficiency, ship sizes are becoming larger. The response of the ship structure is increasingly crucial for assessing ship safety. Conventionally, the hull structure response is usually calculated using linearized hydrodynamic loads, leading to conservative estimation results. Furthermore, although nonlinear impact loads (such as slamming) can be considered by applying the Wagner Theory (Wen et al., 2022) to the linearized numerical model, the low prediction accuracy, especially for the complex 3D geometry, results in poor performance in predicting nonlinear structure responses, which potentially leads to structural damage.
In recent years, comparing with the response of the ship structure, the nonlinear ship motion under high waves have been more researched by numerical simulation. The potential theory-based nonlinear strip method and nonlinear panel method, considering the second order hydrodynamic load caused by the free surface and the square of fluid velocity, have been extensively discussed in literature such as Yasukawa et al. (2018), Liu et al. (2021). Despite their high computational efficiency and generally acceptable prediction accuracy in most cases, these methods fall short in addressing high nonlinearity related to slamming and green water load. Furthermore, the potential theory fails to handle viscosity and turbulence issues at high ship speeds.
