A new adjustment-free damping method for free-surface waves in numerical simulations

Abstract

Simulating free-surface flow around ships in sea waves using RANSE-Methods

usually requires damping of the waves in front of the outlet to avoid reflections. It has been shown, that common damping methods like sponge layer methods deliver a reliable damping for monochromatic waves, but require a parameter adjustment by the user for different wave scales. The paper describes a new wave damping method which delivers results of same accuracy (reflections less than 2%) but does not require a manual user adjustment. The method is based on damping the vertical velocity component to reduce wave propagation. This is done by implicitly relaxing this component to zero. The relaxation is implemented with the deferred correction approach. The method is implemented in our own in-house OpenFOAM solver, which is a RANSE code using the volume of fluid method and a SIMPLE-like algorithm for the solution. Verification is done in 2D for waves of different scales, steepness, computational meshes and damping zone measures. A comparison to a linear sponge layer approach is given for the different wave scales. The 2D simulations show, that the best wave damping is achieved with the same relaxation function parameters for each individual wave. A 3D application to a modern yacht in head waves is presented. All simulation results show that the new method delivers a reliable wave damping without any parameter adjustment. The method is particularly applicable for flows with waves of different scales, like sea waves superposed with the wave system

generated by a yacht.