Analysis of wave focusing characteristics of parabolic reflecting wall

Extraction of energy from the waves has drawn considerable interest due to its abundant availability and predictable characteristics. Although energy is available all along the wave, normal to wave direction, the majority of the existing wave energy converters (WECs) typically capture energy from only a part of it. One of the cost effective and efficient solutions for harnessing incident wave energy is by integrating WECs with the breakwater. It will be more beneficial if the breakwater is designed to gather and focus the energy towards the inlet of a WEC, which improves its efficiency. Therefore, to achieve this purpose, a parabolic wall/breakwater was proposed, which is inspired from the concentrated solar power (CSP) technology. In this study, experiments were conducted to investigate the free surface elevation at different locations in front of the parabolic wall. The results indicate that when the focal point of the parabolic wall matches with 0.5 times the wave length, the wave height at that location reaches up to 4.3 times the incident wave height for regular waves. Additionally, under random wave incidence, the maximum wave amplification at the focal point was observed to reach up to 2.7 times the significant wave height, making it an ideal location for harnessing wave energy. Further, the wave amplification ratio remains consistent for different wave heights at a given relative water depth (<i>d/L</i>), indicating that wave amplification primarily depends on the wave frequency rather than incident wave height. It was also observed that changes in water depth do not significantly impact the maximum wave amplification. These measurements were supported by 3D numerical simulations which were performed using open-source CFD model REEF3D.