The sea is an important resource of renewable energy for its extension and the power conveyed by waves, currents, tides and thermal gradients. Amongst these physical phenomena, sea waves are the source with the highest energy density and may contribute to fulfilling the global increase of power demand. Despite the potential of sea waves, their harnessing is still a technological challenge. One of the simplest and most reliable solutions for the optimal exploitation of this source is represented by the oscillating water column systems operating with Wells turbines. With the aim to predict the operating curves of monoplane isolated Wells turbines, computational fluid dynamics models were developed. A three-dimensional multi-block technique was applied to create the computational domain of the air with a fully mapped mesh composed of hexahedral elements. The employment of circumferential periodic boundary conditions allowed for the reduction of computational power and time. The proposed models use RANS or u-RANS schemes with a multiple reference frame approach or the u-RANS formulation with a sliding mesh approach. In order to validate the implemented models, comparisons of the achieved results and literature analytical and experimental data were performed in environmental conditions typical of the Mediterranean Sea, showing a good agreement.