This study seeks to address the low-frequency limitations in the computation of hydrodynamics for slender ships using strip theory, and develops an efficient method for calculating hydrodynamics over a wider frequency range for slender ships using a simplified approach.

Based on the unified theory of strip theory and ordinary slender body theory, the added mass and damping coefficients of a prolate spheroid, slender, modified Wigley model and S60 ship are calculated programmatically. A comparison is made between the calculated results using the unified theory and experimental data, as well as results obtained from strip theory, 3D translating and pulsating source Green's function method and other methods. The computational characteristics and advantages of the unified theory are then analyzed.

The results indicate that the unified theory based on 2D sections produces results under zero-speed conditions that are consistent with those obtained by the 3D panel method. For conditions involving ship speed, the calculated results exhibit consistent variations with those obtained from the 3D translating and pulsating source Green's function method.

The proposed unified theory is capable of reflecting 3D effects in the low-frequency region, which gives it greater efficiency and simplicity compared to 3D methods, and thus significant practical value.