Unstructured-grid Modeling for Wave Energy Resource Assessment

Model hindcasts of wave climate have been widely recognized in assessing wave energy resource and understanding the temporal and spatial variability in the wave resource. However, there is a challenge to simulate wave climate with localized high resolution in a large model domain. Therefore there is a need to explore the benefits and evaluate the performance of unstructured-grid models for a large wave modeling domain of interests. In this study, the unstructured-grid, third generation spectral wave model - Simulating Waves Nearshore (UNSWAN) was evaluated in a test bed in the central Oregon Coast, with comparison to structured-grid models, such as WaveWatchIII (WWIII). UNSWAN was forced by open boundary input from WaveWatchIII model outputs and wind forcing from NOAA NCEP's Climate Forecast System Reanalysis (CFSR) dataset. The WWIII model outputs were generated by the regional wave models nested with the global wave model. The CFSR winds have 0.5o spatial resolution and 1-hour temporal resolution. The model was validated with observed wave data from National Data Buoy Center (NDBC) buoys within the test bed. Simulated six IEC wave resource parameters using UNSWAN showed a good agreement with observed data. The average root-mean-squared error and correlation coefficient are 0.45 and 0.94 for significant wave height, and 0.96 and 0.91 for energy period respectively. The UNSWAN model can successfully reproduce the temporal variability of wave climate in the test bed. This study shows that unstructured-grid wave modeling provides advantages in computational efficiency and practical approach for simulating wave climates near complex geometries. Potential application of UNSWAN to a regional-scaled model domain is also discussed.