Implementation of a velocity decomposition method coupled with volume-of-fluid method for simulating free-surface flows

An efficient velocity decomposition method (VDM) is proposed for simulating free surface flows based on OpenFOAM platform, which is primarily intended for marine hydrodynamics applications. In this method, it is assumed that the free surface can be treated as a source region, which introduces rotating velocity related to the wave elevation. In the implemented solver called cpVDFoam, the decomposed potential flow velocity is computed by solving the Laplace equation without considering the effect of free surface, and the remaining non-potential velocity is determined with a complimentary Navier-Stokes (N-S) equation. Further, the free surface is modeled using volume-of-fluid (VOF) method in the viscous domain for obtaining the non-potential velocity. Flow field analysis shows that non-potential velocity magnitude contributed by freesurface is positive correlation with wave elevation, and which value shall decrease to zero in the zero wave elevation region. The efficacy of the proposed VDM is validated by comparing the simulation results with the results obtained using standard OpenFOAM solver interFoam and earlier reported experiment. All results indicate that the present method exhibited similar accuracy as the conventional CFD method but less sensitive to the domain size.