High-fidelity Simulation of Air Entrainment in Breaking Wave Impacts

Global climate change is increasing the odds of more extreme weather events taking place which will have higher intensity and longer duration. Strong winds and high sea levels generate more large waves and drive them much closer to the UK's shore than before. The coastline, offshore platforms, renewable energy converters and marine vessels are battered by storms, and their integrity is placed under the threat of violent wave impact. Such extreme events also challenge the emergency landing of aircraft in the sea particularly ditching helicopters as well as the launch and recovery operations of lifeboats from larger vessels under high sea states.

To mitigate the uncertainties and risks posed by such natural hazards on the public safety and the economic activity of the UK, it is vital for research, industry and governmental bodies to improve the design of coastal and offshore structures through the accurate prediction of the extreme wave loadings and the resultant damage by the development and use of high-fidelity new generation free surface modelling tools, which combine mathematical and physical science as well as the latest software engineering technology.

The overall aim of this project is to develop such a powerful numerical tool to enable academics and industrial users to gain new scientific insights and better understanding of the air entrainment process in wave breaking. This will help determine the critical aeration level and distribution before/within/after wave breaking, and predict the characteristics of the resultant impact loadings on coastal and offshore structures through CFD simulation. This will be accomplished by re-engineering and extending the capabilities of an existing novel compressible multiphase hydro-code incorporating an advanced two-fluid hybrid turbulence modelling approach, fluid surface tension and adaptive high order numerical discretisation schemes deployed by state-of-the-art HPC facilities.

The availability and use of the tools and data produced by the project will firmly support academics and engineers to modify/improve the designs of crucial defence systems in order to address increasing environmental challenges, protect valuable personal and public assets, safeguard local residents and commuters, and ensure the integrity of transport lines. This will help to maintain the economic-environmental-societal competitiveness and long-term sustainable development of the UK.

The proposed research will enable a close and detailed examination of air entrainment into breaking waves impacting coastal structures, offshore platforms and marine renewables, marine vessels and ditching aircraft to gain new insights and to advance understanding of the underlying complex physics through the development and use of a new-generation free surface modelling tool.

The developed tool and produced data will empower research, industry and governmental bodies to modify/improve the design of coastal defence systems and offshore structures to mitigate harsh environmental challenges. This has direct economical-societal benefits for communities living and/or travelling near the coastal regions: by protecting valuable personnel and public assets and safeguarding local residents and commuters. It will also help to ensure the integrity of transport lines to support the sustainable economic development of the UK. Other direct beneficiaries from the development of the numerical tool will be academics, engineers and policy makers in the areas Maritime and Aviation Safety, where the uncertainties in the safe operation of vessels/aircraft associated with the complex structure-wave-air interaction could be substantially reduced. The passengers and crew on-board will directly benefit from the improved safe operation. The developed numerical tool will also benefit the research community working in the area involving compressible multiphase flows.

To maximise the impact of the project, a number of routes to disseminate the potential impact of the project have been identified. These include (1) early engagement with stakeholders, (2) networking with the national CCP-WSI research/industry community, (3) disseminating the research outcomes in leading academic journals, (4) public engagement and social-networking and (5) broadcasting outside the UK, with details presented in the Pathways to Impact document.