Solution and domain decomposition model for marine hydrodynamics: rans and potential flow coupling

Abstract

This paper presents a CFD decomposition model for free surface, viscous, in-

compressible flows related to marine hydrodynamics. The solution decomposition is based

on Spectral Wave Explicit Navier Stokes Equations (SWENSE), where the primitive vari- ables are written as the combination of incident and diffracted fields. This allows efficient coupling of the discretised Navier–Stokes free surface flow equations with arbitrary poten- tial flow theories. The domain decomposition is achieved with implicit relaxation zones in order to prevent undesirable wave reflection in unbounded domains. Interface captur- ing is obtained with implicitly redistanced Level Set (LS) method derived from Phase Field equation. This approach removes the need to redistance the LS field using conven- tional redistancing procedures and reduces mass conservation issues fundamental to the LS method. The numerical model is based on a polyhedral, second-order accurate, col- located finite volume method (FVM). The coupling of primitive variables is obtained via segregated solution algorithm based on SIMPLE and PISO. The model is implemented in OpenFOAM. The verification of the model is performed by a number of two–dimensional (2–D) test cases. The reflection analysis is carried out by changing the relaxation zone length. Mass conservation and preservation of the signed distance LS function is demon- strated with a simulation lasting 50 incident wave periods. A long domain simulation is also carried out to show that the damping of the wave does not occur. Finally, a wave steepness study has been carried out by changing wave height while the wave period was kept fixed. Three–dimensional (3–D) test cases regarding higher order forces on circular cylinder have also been carried out. However, the results will be presented in future work.