Hydrodynamics of Oscillating Water Columns Integrated in Breakwaters

Abstract

This thesis explores the integration of Oscillating Water Columns (OWCs) into breakwaters, leveraging the dual functionality of wave energy conversion and coastal protection. A combination of extensive experimental datasets and numerical simulations was used to assess the effects of design configurations on performance. The work offers key insights into the physical mechanisms governing OWC behaviour, emphasises the importance of design optimisation, and contributes to guidelines for efficient renewable energy deployment.

A novel power estimation method is introduced to improve the accuracy of physical modelling. In parallel, a rigorous uncertainty analysis systematically identifies and quantifies key sources of uncertainty. The findings of this work provide critical guidance for improving the reliability and precision of OWC experimental evaluations. Together, these advancements establish a robust framework for subsequent analyses.

Using this framework, an extensive experimental dataset was generated to examine the effects of key geometric parameters, including: (a) breakwater geometry, (b) pneumatic efficiency, (c) chamber geometry, (d) chamber positioning, and (e) front and back wall designs. Performance was assessed in terms of energy capture and shoreline protection. The findings provide valuable insights for the design and development of more efficient OWC-breakwaters.

Complementary computational fluid dynamics (CFD) simulations, validated against experiments, examined turbulence-induced energy dissipation and scale effects. The results reveal that front-wall profiles significantly affect turbulence and overall efficiency, while scale effects were found to be minimal, suggesting the feasibility of fine-tuning draft designs at laboratory scales as a practical measure.

Finally, this thesis examined device performance under a wide range of random wave conditions and investigated the probabilistic nature of the energy conversion process. Specifically, it analysed the peaks of the OWC’s power output and proposed a Gamma distribution model to effectively predict its probability density function. The results provide valuable insights for optimising OWC designs for real-sea conditions.