A Field Experiment on Wave Forces on an Energy-Absorbing Breakwater

Abstract

The U-OWC is a caisson breakwater embodying a device for wave energy absorption. Under the wave action, the pressure acting on the upper opening of the vertical duct fluctuates, producing a water discharge alternatively entering/exiting the plant through the U-duct, formed by the duct and the chamber. The interaction between incoming waves and the water discharge alters the wave pressure distribution along the wave-beaten wall of this breakwater compared with the pressure distributions on a vertical pure reflecting wall. As a consequence, the horizontal wave forces produced on the breakwater are also different. A small scale U-OWC breakwater was put off the eastern coast of the Strait of Messina (Southern Italy) to measure the horizontal wave force. Experimental results were compared with Boccotti’s and Goda’s wave pressure formulas, carried out for conventional upright breakwaters, to check their applicability on the U-OWC breakwaters. Both models are suitable for design of U-OWC breakwaters even if they tend to overestimate by up to 25% the actual horizontal loads on the breakwater. Indeed, the greater the absorption of the energy is, the lower the wave pressure on the breakwater wall is.

Numerical Study on Hydrodynamics of Submerged Permeable Breakwater under Impacts of Focused Wave Groups Using a Nonhydrostatic Wave Model

“…To prevent coastal infrastructure and communities from the devastating power of huge surges and waves during hurricanes and tsunamis [23][24][25], many coastal defense structures were built along the coastline. As one of the most common coastal defense infrastructures, breakwaters were widely constructed [26][27][28][29][30]. Although the emergent breakwater can effectively dissipate the incident wave energy and the transmitted wave components can be below the acceptable limits for keeping the stability of coastal regions, they can cause some environmental problems, such as the impact on seascapes.…”