Objectives Viscous flow numerical simulation is widely applied in ship hull design for its high precision in capturing complex flow field characteristics, but it suffers from high computational resource consumption and long calculation time, which restricts its efficiency in ship motion prediction and optimal design. To address this problem, this study combines potential flow and viscous flow theories to establish a viscous-potential flow coupling method for ship motion prediction, and systematically analyzes the computational efficiency advantages of this method under different wave environments, aiming to provide technical support for balancing simulation accuracy and computational resources in intelligent ship design.

Methods Taking the Wigley-III ship model with a scale ratio of 1:50 as the research object, the flow field around the hull was divided into an outer potential flow region and an inner viscous flow region by using the domain decomposition method, and a coupling interface was set at their junction to realize the efficient transmission of wave data. The potential flow region adopted the Boussinesq approximation and SWENSE field decomposition method to generate waves, while the inner viscous flow region used the RANS-VOF method combined with the SST k-ω turbulence model to simulate the interaction between the ship and waves. Different wave height and wavelength conditions were designed, and the heave and pitch motions of the ship were analyzed. The simulation results were compared with model test data and full viscous flow simulation results to verify the reliability of the coupling method. Meanwhile, indicators such as calculation time, grid demand, computational efficiency, and speed-up ratio were statistically analyzed, and the distribution characteristics of these indicators under different wave steepness were explored.

Results The results show that the viscous-potential flow coupling method has excellent stability in the energy transmission between inner and outer wave domains, with a relative error of less than 1.03% under different wave heights and wavelengths. The ship motion simulation results are basically consistent with the test data, and the relative error of heave and pitch is within 5.14% -10.99% and 5.83% -11.64% respectively, which is close to or even better than the full viscous flow simulation results under some working conditions. In terms of computational efficiency, the grid demand of the coupling method is only 0.39 -0.47 times that of the viscous flow method, and the average calculation time is shortened by 38.51%. The average computational efficiency is increased by 86.8%, and the average speed-up ratio is 0.862. However, the efficiency advantage is environment-sensitive: when the wave steepness increases from 0.013 to 0.021, the speed-up ratio increases significantly; when the wave steepness exceeds 0.021, the speed-up ratio oscillates and decreases due to the enhancement of wave nonlinearity.

Conclusions The viscous-potential flow coupling method can meet general engineering needs for ship motion simulation with high reliability. It has obvious computational efficiency advantages, greatly reducing the computational cost. Its efficiency advantage is sensitive to wave conditions, and the optimal application strategy should be formulated based on wave steepness characteristics. This study helps to establish an autonomous trade-off mechanism between accuracy and computational resources in future ship optimization, and promotes the intelligent development of ship design.