Mixed time-frequency-domain method for nonlinear hybrid floating breakwater-WEC

Ocean waves represent a vast and renewable resource that is prevalent across the globe. However, the relentless erosion of marine equipment and coastal structures poses an ongoing challenge to safety. The integration of a floating breakwater with a wave energy converter (FB-WEC) offers a dual solution that addresses both wave protection and energy harnessing. The attenuation of lowfrequency ocean waves and their subsequent energy capture is a critical issue within the field of ocean engineering. The introduction of additional nonlinear stiffness can significantly enhance the low-frequency response of FB-WECs without the need to enlarge their physical dimensions. To address the complex nonlinear fluid-structure interactions inherent in nonlinear FB-WECs, a hybrid time-frequency domain approach has been developed. This method is based on the concept of harmonic decomposition and enables the rapid computation of the FB-WEC's motion response while facilitating the concurrent acquisition of wave data. An innovative umbrella-type bistable mechanism (U-BM) has been conceived and implemented in the FB-WEC design. A prototype has been fabricated, and its performance was tested through wave flume experiments. The results of these experiments have validated the numerical simulations, confirming that the UBM FB-WEC is proficient at responding to low-amplitude wave excitations. Under conditions of comparable wave height, the U-BM FB-WEC consistently delivers over 50% more power output in the low-frequency band compared to its linear counterpart. This advancement marks a significant stride in the field of wave energy conversion, promising more efficient energy capture and a more sustainable future for marine environments and coastal communities.