Numerical analysis of the interaction of irregular waves with two dimensional permeable coastal structures

This paper will address the validation and application of a volume of fluid method for coastal structures under the influence of normal incident irregular wave fields. Several physical processes will be addressed as part of the validation process, namely: (i)wave reflection from permeable and impermeable structures, (ii) wave transformation over a small shoal, (iii) wave damping inside of a permeable structure, (iv) the resulting wave induced internal setup and (v)wave induced forces. The numerical model will be validated against a multiple of experimental data sets for two dimensional coastal problems. The impact of air-relief gaps on the modelled wave induced pressures on a crest wall is analysed for the two dimensional layout of the structure. This is analysed to study the importance of the cushion effect from the incompressible air phase. Subsequent to the validation of the numerical model the internal setup in permeable coastal structures is given separate attention. A combination of an analytical prediction of the magnitude of the internal setup and numerical results is used to derive numerically based empirical formulae for the magnitude and the time scale of the internal setup. The formulae include the effects of wave height, wave period, material properties of the coastal structure and the dimensions of the structure. The numerical model is based on the OpenFoam® CFD-toolbox. •OpenFoam/waves2Foam is found to correctly transform irregular waves.•The model correctly predicts reflection and wave damping of irregular waves.•Numerically based empirical relationship for internal setup is provided.•The impact of air on prediction of wave-induced forces is analysed.