This paper generalises existing approaches for free-surface wave damping via momentum sinks for flow simulations based on the Navier-Stokes equations. It is shown in 2D flow simulations that, to obtain reliable wave damping, the coefficients in the damping functions must be adjusted to the wave parameters. A scaling law for selecting these damping coefficients is presented, which enables similarity of the damping in model and full scale. The influence of the thickness of the damping layer, the wave steepness, the mesh fineness and the choice of the damping coefficients are examined. An efficient approach for estimating the optimal damping setup is presented. Results of 3D ship resistance computations show that the scaling laws apply to such simulations as well, so the damping coefficients should be adjusted for every simulation to ensure convergence of the solution in both model and full scale. Finally, practical recommendations for the setup of reliable damping in flow simulations with regular and irregular free-surface waves are given.

The further development of the first-order panel method panMARE for simulating floating offshore wind turbines (FOWTs) in time domain is presented in this work. Based on a surface discretisation of platform, tower and rotor with its wake, the three-dimensional aerodynamic and hydrodynamic flow fields are calculated. A free wake deformation model is integrated to capture blade–wake interaction. Hydrodynamic, aerodynamic and mooring loads are cumulated by a six-degrees-of-freedom solver to compute the motion of the FOWT. The presented method is able to simulate unsteady and aperiodic motions and to predict the wake deformations and their influence on the rotor loads due to the platform motion. In order to verify the method, simulation results of the DeepCWind floater with the NREL 5-MW baseline turbine are compared with those obtained in the OC4 project. The ability to capture highly unsteady situations is studied as well by simulating a gust with varying length.