The contribution of ocean wave energy as a renewable energy source is increasing. However, more research needs to be carried out to make wave energy a valiable alternative for the conventional energy sources. This paper gives a detailed description of the numerical tool that is used to study the hydrodynamic behavior of wave energy converters based on wave overtopping. In first instance, this numerical tool will be used to determine the overtopping volumes on a wave-by-wave level. Physical model tests have been carried out to validate the numerical model for this application. The physical model test set-up is also described in detail in this paper.