Representing Wave Energy Converters in the SWAN model with varying transmission coefficients across frequencies

Abstract

Understanding the effects of arrays of Wave Energy Converters (WEC) on the wave fields is still an ongoing effort. Many publications have proposed different approaches to incorporate WEC farms in wave models to assess sea state changes in the near and far field. In the present study, a practical iterative method is proposed to incorporate the spectral response of a WEC obtained from the HAMS-MREL Boundary Element Model (BEM) in the SWAN spectral wave model. This allows to change the transmission and reflection properties of the WEC, represented in the model as an obstacle, at each time step. Since the response of a WEC simulated in the BEM model is defined in the frequency domain, it is possible to relate the absorbed power, at each discrete frequency, to the transmission coefficient applied at each frequency used to discretize the wave spectrum in SWAN. In this case, the method is applied to a single point-absorber type device since its response is independent of the waves’ directions. Validation of the method is done comparing the omnidirectional spectrum obtained downwave of the WEC in SWAN, with the spectrum reconstructed using the regular wave fields information (for each frequency) obtained in HAMS-MREL.