Development of an oscillating water column-type wave absorber for anti-reflection and effective energy extraction

Assorted novel low-reflection structures have been developed for the need of berthing safety in the harbor. The oscillating water column (OWC)-type wave absorbers offer significant benefits as they not only reduce reflected waves but also harness wave energy effectively. Based on the previous studies, a multi-factor comprehensive research on the reflection characteristics, energy extraction performance as well as the wave power dissipation of OWC-type wave absorbers is carried out. The influence of opening ratios is the key point, and the coupled effects of it with the incident wave height and the front wall draft on the hydrodynamic characteristics of the OWC are further investigated. The results indicate that though a larger opening ratio results in a smaller valley value of wave reflection coefficient within the experimental wave frequency range, an appropriate opening ratio can weaken the sensitivity of the reflection behavior of OWC to wave frequency and widens the low reflection frequency band. The existence of vortex-dissipated energy leads to a difference in the wave frequencies corresponding to the minimal wave reflection and maximum extraction efficiency. Besides, reducing the front wall draft is preferred in enhancing efficiency and reducing wave reflection, and meantime this will be accompanied by a shift in resonant frequency. A decrease in wave height has a similar effect, but the effect is not as significant as the change in the draft. The increase of wave height will cripple anti-reflection performance due to the enhancement of radiated wave energy. The OWC-type wave absorber is convincingly competitive in terms of low wave reflection, compared with other extensively studied breakwaters.