Improvements in the numerical modelling of wake effects for wave energy converter farms

Ocean Energy Europe has estimated that 100 GW of ocean energy capacity (wave and tidal) could be deployed in Europe by 2050. Along with these European targets it is expected that large farms of Wave Energy Converters (WECs) will be installed in the sea and as part of the consenting process it will be necessary to quantify their impact on the local environment. The physics of the wave field around the WEC farm is important since it affects coastal processes and potentially marine activities located near by. Thus it will be mandatory to accurately quantify the local changes generated by the presence of a WEC farm and assess the significance of its impact. To address these concerns, the objective of this thesis is to improve the available numerical methodologies to assess wake effects for WEC farms in order to quantify their impact on the surrounding wave field. Two different methodologies have been developed in order to better represent WECs in wave propagation models (WPMs), the type of model to resolve wave transformation processes. The two methodologies use a WPM based on the mild-slope equations to solve the wave propagation across large domains and a wave-structure interaction Boundary Element Method (BEM) solver to assess the near-field wave-body interaction phenomenon. The first method is based on a representation of the WECs as obstacle cells that are tuned based on the wave field obtained from the BEM solver. The second method looks into the description of the wave perturbation generated by the WEC by coupling the results obtained from the BEM solver into the WPM as an internal boundary condition. The methods accuracy is assessed together with case scenarios accounting for realistic environmental conditions such as irregular sea states and irregular bathymetries. Thus, as part of the accomplishments of this thesis two innovative numerical methodologies were developed, which include the main transformation processes surrounding a WEC farm for medium scale domains using realistic bathymetries