A numerical model is presented for the estimation of Wave Energy Converter (WEC) performance in variable bathymetry regions, taking into account the interaction of the floating units with the bottom topography. The proposed method is based on a coupled-mode model for the propagation of the water waves over the general bottom topography, in combination with a Boundary Element Method for the treatment of the diffraction/radiation problems and the evaluation of the flow details on the local scale of the energy absorbers. An important feature of the present method is that it is free of mild bottom slope assumptions and restrictions and it is able to resolve the 3D wave field all over the water column, in variable bathymetry regions including the interactions of floating bodies of general shape. Numerical results are presented concerning the wave field and the power output of a single device in inhomogeneous environment, focusing on the effect of the shape of the floater. Extensions of the method to treat the WEC arrays in variable bathymetry regions are also presented and discussed.modes may have a significant impact on the wave phase evolution during propagation. Such a fact was demonstrated through the interference process in one-directional wave propagation as observed for either varying topographies (see e.g., [12,13]) or abrupt bathymetries including coastal structures (see e.g., [14][15][16]). For such problems, the consistent coupled-mode theory has been developed in [17], for the water waves propagation in variable bathymetry regions. Furthermore, it was subsequently extended for 3D bathymetry in [18], and applied successfully to treat the wave transformation over nearshore/coastal sites with steep 3D bottom features, like underwater canyons; see, e.g., [19,20].In recent works [21,22] the coupled-mode model is further extended to treat the wave-current-seabed interaction problem, with application to the wave scattering by non-homogeneous current over general bottom topography. The problem of the directional spectrum transformation of an incident wave system over a region of strongly varying three-dimensional bottom topography is further studied in [22]. The accuracy and efficiency of the coupled-mode method is tested, comparing numerical predictions against experimental data by [23] and calculations by the phase-averaged model SWAN [24,25]. Results are shown in various representative test cases demonstrating the importance of the first evanescent modes and the additional sloping-bottom mode when the bottom slope is not negligible.In this work, a methodology is presented to treat the propagation-diffraction-radiation problem locally around each WEC, supporting the calculation of the interaction effects of the floating units with variable bottom topography at a local scale. The method is based on the coupled-mode model developed by [17], and extended to 3D by [18], for water wave propagation over general bottom topography, in conjunction with the Boundary Element Method (BEM) for the hydrodynamic analysis of fl...

In the present work a hybrid boundary element method is used, in conjunction with a coupled mode model and perfectly matched layer model, for obtaining the solution of the propagation/diffraction/radiation problems of floating bodies in variable bathymetry regions. The implemented methodology is free of mild-slope assumptions and restrictions. The present work extends previous results concerning heaving floaters over a region of general bottom topography in the case of generally shaped wave energy converters (WECs) operating in multiple degrees of freedom. Numerical results concerning the details of the wave field and the power output are presented, and the effects of WEC shape on the optimization of power extraction are discussed. It is demonstrated that consideration of heave in combination with pitch oscillation modes leads to a possible increase of the WEC performance.

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A variety of devices and concepts have been proposed and thoroughly investigated for the exploitation of renewable wave energy. Many of the devices operate in nearshore and coastal regions, and thus, variable bathymetry could have significant effects on their performance. In particular, Oscillating Wave Surge Converters (OWSCs) exploit the horizontal motion of water waves interacting with the flap of the device. In this work, a Boundary Element Method (BEM) is developed, and applied to the investigation of variable bathymetry effects on the performance of a simplified 2D model of a surge-type wave energy converter excited by harmonic incident waves. Numerical results, illustrating the effects of depth variation in conjunction with other parameters, like inertia and power-take-off, on the performance of the device, are presented. Finally, a comparative evaluation of the present simplified surge-type WEC model and point absorbers is presented for a case study in a selected coastal site on the Greek nearshore area, characterized by relatively increased wave energy potential.

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