Wavecat® wave energy converter modelling by means of a RANS-VoF numerical model

The Wave Cat Wave Energy Converter is a floating structure formed by two hulls (like a catamaran), but unlike a catamaran the hulls are not parallel, they converge from bow towards stern. Its principle of wave energy capturing is wave overtopping, the incident waves are propagating between the wedge formed by the two hulls and they eventually overtop the freeboard, the water is collected in reservoirs placed on deck and the difference between the water level inside the reservoirs and the mean sea level is taken into advantage to propel ultra-low head turbines. Physical model tests were performed in order to validate and develop the basic concept, small and medium scale experiments with a fixed and a floating model respectively. In addition a numerical model was developed, RANS-VoF models were employed; the model solves the RANS (Reynolds Averaged Navier Stokes) equations with a Volume-of-Fluid approach (in order to track the free surface position). The goal of the model is conducting the optimization of the device. In this sense a numerical wave tank as well as a 2D fixed model were validated and both 3D fixed and floating models were implemented. Detailed methodology about the implementation and validation of these models is presented in this paper.