The vast ocean surface populated by wind-generated waves is where atmosphere and ocean interact. It is also where maritime and offshore renewable energy industries have to operate to secure future sustainable energy. Wave breaking provides the upper limit to how large waves may become and is the mechanism for how they dissipate energy. Breaking in crossing seas, the harshest conditions for shipping and offshore renewable energy (ORE) design, is poorly understood. A recent case study of the famous Draupner rogue wave by four of the investigators (M.L. McAllister et al. (2019) Laboratory recreation of the Draupner wave and the role of breaking in crossing seas. J. Fluid Mech. 860, 767-786) has shown that breaking in such seas is fundamentally different: it limits maximum wave height much less and is potentially much less dissipative. As a consequence, existing breaking criteria as implemented in wave forecasting tools and offshore design guidelines are not valid and unreliable in crossing seas.

Through collaboration with DNV GL (an international accredited registrar and classification society), the European Centre for Medium-Range Weather Forecasts (a world-leading operational wave forecasting agency) and Shanghai Jiao Tong University (ranked first in the world for ocean engineering in the Shanghai Ranking), this project aims to develop and experimentally and numerically validate robust new wave breaking and dissipation criteria appropriate for highly directionally spread and crossing-sea conditions and implement these in wave forecasting tools and offshore design guidelines.

The UK and Ireland possess substantial offshore wind resources that are capable of making major contributions to their national and international energy supply. A key problem in developing such resources is designing against the harsh ocean environment that prevails in the territorial waters of both countries. The design challenge is even greater in China (with an estimated 100bn offshore wind market), where candidate sites for offshore wind farms are exposed to typhoons, in which crossing sea conditions have an increased likelihood.

The proposal will address this challenge through extensive large-scale experiments in two globally unique wave, FloWave at the University of Edinburgh (part of the UK ORE testing infrastructure) and the Ocean Basin at Shanghai Jiao Tong University, state-of-the-art numerical simulations and the development of new theory. The 30-month proposal has an investigating team across four universities (Oxford, Edinburgh, Manchester and University College Dublin) consisting of a PI, four Co-Is and a Researcher Co-I, three of whom are early-career researchers.