Absorption of wave reflections in way of an inlet boundary

In recent years, Computational Fluid Dynamics (CFD) is increasingly becoming
more attractive for the analysis of ship seakeeping. This is because of the increasing efficiency of computers and the accuracy of solvers (e.g. Reynold Navier Stokes Averaged – RANS) that may be more accurate in terms of idealizing nonlinear phenomena in comparison to potential flow methods. Notwithstanding this, RANS methods remain sensitive to accurate wave modelling across the fluid domain as well as the reflection of domain boundaries. This paper studies the effective absorption of the reflected waves from a structure heading back towards the inlet boundary with a relaxation zone method. This is achieved by applying the RANS CFD solver OpenFOAM-v2206 and wave generation toolbox waves2Foam. The modelled case is a 2D box in waves with different wave lengths. The distance of the relaxation zone and the distance after the relaxation zone until the box varies and their effect to excitation forces is studied. It is demonstrated that longer distances reduce the problems caused by wave reflections. The effects are reduced with coarser meshes as the mesh itself dampens the waves.