Introduction  Accurate calculation of the hydrodynamic coefficients for floating structures and the investigation of the flow field distribution around floating bodies on the marine free surface are essential for improving the engineering design and application of marine structures.

  Method  This study utilized the computational fluid dynamics (CFD) approach and the Reynolds Averaged Navier-Stokes (RANS) method and considered the effects of viscosity and free surface interactions on the hydrodynamic behavior of floating structures. By employing the dynamic mesh technique, this study simulated the periodic movements of simplified three-dimensional (3D) shapes: spheres, cylinders, and cubes, which were representative of complex marine structures. The volume of fluid (VOF) method was leveraged to accurately track the nonlinear behavior of the free surface. In this analysis, the added mass and damping coefficients for the fundamental modes of motion (surge, heave, and roll) were calculated across a spectrum of frequencies, facilitating the fast determination of hydrodynamic forces and moments exerted on floating structures.

  Result  The results of this study are not only consistent with the results of the 3D potential flow theory but also further reflect the role of viscosity. This method can be used for precise calculation of the hydrodynamic coefficients of floating structures and for describing the flow field of such structures in motion on a free surface.

  Conclusion  The methodology presented goes beyond the traditional potential flow approach.