New Study Shows that Ocean Waves can Grow Way Beyond Known Limits

24 September 2024

Research published in Nature by Trinity Engineering Lecturer Mark McAllister has shown that when waves are three-dimensional as opposed to two-dimensional, they can be twice as steep before they break and continue to grow even steeper after breaking has occurred. 

When waves in the ocean become steep, they break. This process of wave breaking is complex and not fully understood. Wave breaking has broad implications from how offshore structures are designed to weather forecasting and climate modelling. One significant issue with our understanding of wave breaking is that in the past it has often been assumed that waves are two-dimensional. This assumption was necessary to simplify the way in which waves are studied, either theoretically or in computer and experimental models.  However, in the oceans waves can travel in many directions and are not two-dimensional. 

A new experimental study led by Dr McAllister of Oxford’s Department of Engineering and and Prof. Ton van den Bremer of the universities of Oxford and Delft studied how the three-dimensionality or ‘directional-spreading’ of ocean waves affects when they break. The new study featured an international team of researchers based at the University of Oxford, University of Edinburgh, University of Manchester, University College Dublin, Université Paris-Saclay and TU Delft.

The results of the study show that three-dimensionally spread waves can become twice as steep as two-dimensional waves before they break. The researchers also found that while conventional waves break and form white caps which stop them growing further, waves with high directional spreading can keep growing when they break. These enormous waves can grow to four times the conventional limiting steepness while breaking.

The knowledge that multidirectional waves can become as much as four times larger than was deemed possible in 2D can help design safer marine structures. ‘The three-dimensionality of waves is often overlooked in the design of offshore wind turbines and other structures in general. Our findings suggest that this could lead to designs that are less reliable’, says Professor McAllister.

The experiments were made possible by the unique shape the FloWave circular wave basin, part of the Ocean Energy Research Facility in Edinburgh, alongside the development new measurements methods.