Modelling Extreme Free-Surface Flows: applications to breaking waves, wave-structure and wave-vessel interactions

Lead Research Organisation: Imperial College London
Department Name: Civil & Environmental Engineering

Abstract

The proposed research concerns the description of extreme free-surface flows with applications in both deep water offshore and the shallow water coastal locations. The work will involve the development of a new numerical model appropriate to the description of large surface water waves and their interaction with both fixed structures and floating vessels. The key feature linking these flows will be the occurrence of wave breaking; involving the break-up of the water surface, the entrainment of air and the rapid development of areas of highly turbulent flow. From a practical perspective such flows are extremely important because they are associated with the highest (limiting) water surface elevations, the largest water particle velocities and the maximum applied fluid loads. As a result, they are directly relevant to the design of all manner of marine structures and vessels.In order to simulate such flows, and in so doing provide improved physical understanding, the new numerical model will combine the advantages of two very different modelling procedures: a Boundary Element Method applied before the onset of wave breaking and Smooth Particle Hydrodynamics applied to the breaking and post-breaking fluid flow. By combining these procedures the proposed method will seek to create a robust and accurate model capable of describing a wide range of free-surface flows; particular attention being paid to those aspects of wave-structure and wave-vessel interactions that are critical for design and cannot be described by existing solution procedures.The model predictions will be validated against new laboratory observations. This will involve the use of scaled physical model tests and will consider a wide range of practically important fluid flows including:(i) Breaking waves, including both large-scale over-turning and spilling waves;(ii) Highly nonlinear effects in wave-structure interaction, including high-frequency wave scattering, vertical jetting where fluid is projected upwards to very high elevations creating wave-in-deck loads, and wave slamming on both vertical columns and the deck structure;(iii) Wave-vessel interactions, particularly the occurrence of green water inundation and large impact forces.In tackling these problems, the combined experimental and numerical studies will seek to provide new physical understanding of when and why these events occur, to assess their practical implications and to identify how they can best be modelled in engineering practice.The proposed work is relevant to a wide range of problems in fluid mechanics, with particular application to the effective design and safe operation of marine structures. Direct support from three key industrial practitioners is incorporated within the proposal. The project will also be relevant to the renewable energy industry. With interest in locating offshore wind farms in areas of high wind and therefore large wave activity, such structures are very susceptible to large-scale wave breaking and the associated impact forces. The shipping industry will also benefit from this project: the new model providing information to improve the design and/or safe operation of vessels to both increase survivability and, in the case of oil tankers, limit the potential for large-scale environmental impact and damage. Finally, the work also has a truly multi-disciplinary contribution, beyond the coastal/offshore/navel architecture boundaries, in the sense that the break-up of the water surface (specifically the entrainment of air) has implications for air-sea interactions in general, and mass exchange (CO2 absorption) in particular. Such issues are of fundamental importance to oceanographers studying the transfer processes at the ocean surface and contribute a key element to climate change modelling.

Publications

10 25 50
 
Description Improved methods of wave modelling, including:
- Crest heights,
- Wave heights,
- The role of directionality,
- The occurrence of wave breaking,
- The extreme water particle kinematics.
Applying these models into load calculations has highlighted the non-conservatisms associated with present design practice.
Exploitation Route By their incorporation into industry standards and design guidelines. This is presently on-going.
Sectors Aerospace, Defence and Marine,Energy

 
Description Provided the basis for two new Joint Industry Funded Projects. Led to four industrially funded projects to asses the practical implications of the results in relation to the safety and reliability of specific offshore structures Led to a new methodology for the assessment of wave-in-deck loads. Presently being incorporated within the industry standard (ISO and API) design guidelines.
First Year Of Impact 2012
Sector Aerospace, Defence and Marine,Energy
Impact Types Economic,Policy & public services

 
Description Incorporation into the relevant International Standards Organisation (ISO) guidlines for the design of offshore structures
Geographic Reach Multiple continents/international 
Policy Influence Type Participation in a advisory committee
Impact Improved design guidance leads to a reduced risk of failure, with both health and safety and economic implications
 
Description EPSRC (SUPERGEN) research grant: Modelling MRE devices; designing for survivability
Amount £1,039,617 (GBP)
Funding ID EP/J010197/1 
Organisation Engineering and Physical Sciences Research Council (EPSRC) 
Sector Public
Country United Kingdom
Start 06/2012 
End 06/2015
 
Description Industrial CASE Award with BP. Submarine piplines: fluid-structure interactions and fluid loading
Amount £92,667 (GBP)
Funding ID Industrial CASE: voucher number 14220039 
Organisation BP (British Petroleum) 
Sector Private
Country United Kingdom
Start 10/2014 
End 03/2018
 
Description Industrial CASE Award with BP. Wave breaking and the effect of wave-current interactions
Amount £107,560 (GBP)
Funding ID Industrial CASE: voucher number 15220049 
Organisation BP (British Petroleum) 
Department BP Exploration Company
Sector Private
Country United Kingdom
Start 09/2016 
End 03/2020
 
Description Industrial CASE Award with Shell. Wave vessel interactions and the occurrence of wave impacts
Amount £107,560 (GBP)
Funding ID Industrial CASE voucher number 16000155 
Organisation Shell Global Solutions International BV 
Department Shell Research Ltd
Sector Private
Country United Kingdom
Start 10/2016 
End 04/2020
 
Description Industrial CASE award with BP: wave crest kinematics and extreme fluid loads
Amount £96,063 (GBP)
Funding ID BP INDUSTRIAL CASE award: Voucher Number 10000464 
Organisation BP (British Petroleum) 
Sector Private
Country United Kingdom
Start 10/2011 
End 03/2015
 
Description Industrial funding from BP: combined wave-current flows
Amount £120,000 (GBP)
Organisation BP (British Petroleum) 
Department BP Marine
Sector Private
Country United Kingdom
Start 12/2014 
End 12/2016
 
Description Industrial funding: LOWISH JIP
Amount £155,000 (GBP)
Organisation Shell Global Solutions International BV 
Department Shell Research Ltd
Sector Private
Country United Kingdom
Start 10/2014 
End 09/2016
 
Description Royal Society International Exchange Grant: The occurrence and intensity of surface wave breaking in realistic seas
Amount £12,000 (GBP)
Organisation The Royal Society 
Sector Charity/Non Profit
Country United Kingdom
Start 03/2015 
End 03/2017
 
Description Royal Society International Fellowship
Amount £66,000 (GBP)
Funding ID NF 160872 
Organisation The Royal Society 
Sector Charity/Non Profit
Country United Kingdom
Start 01/2017 
End 12/2019
 
Description Wave-vessel interactions
Amount £200,000 (GBP)
Organisation Hyundai Heavy Industries, Ship Hydrodynamics Research Dept. 
Sector Private
Country Korea, Republic of
Start 03/2017 
End 08/2020
 
Description Joint Industry Project: Limits on waves in shallow water (LOWISH) 
Organisation Shell Global Solutions International BV
Department Shell Research Ltd
Country United Kingdom 
Sector Private 
PI Contribution Laboratory observations of extreme waves in shallow water Improved understanding of wave breaking
Collaborator Contribution Provision of field data
Impact New descriptions of shallow water wave statistics New laboratory data base concerning large waves in shallow water Improved models for shallow water wave kinematics
Start Year 2014
 
Description Joint Industry Project: SHORTCREST 
Organisation Maritime Research Institute Netherlands
Country Netherlands 
Sector Public 
PI Contribution Assessment of exiting crest height models and the development of new models Understanding the role of directional spreading and incorporating it in design practice Improved wave modelling, particularly extreme kinematics high in the crests of large waves
Collaborator Contribution The provision of field data Laboratory data at complementary scales
Impact Improved models of extreme ocean waves An assessment of their importance for design applications Recommendations for updated codes of practice (ISO and API)
Start Year 2011
 
Description Wave breaking: 
Organisation Scripps Research Institute
Country United States 
Sector Charity/Non Profit 
PI Contribution Improved methods of wave generation Improved models of wave breaking and energy dissipation Insights into deep water crest height statistics
Collaborator Contribution Flow visualisation techniques Bubble plume analysis methods Linkage between the white cap foam area and the energy dissipation associated with breaking.
Impact New models for wave breaking and the associated wave energy dissipation
Start Year 2015
 
Description Industrial seminar series 
Form Of Engagement Activity A talk or presentation
Part Of Official Scheme? No
Geographic Reach International
Primary Audience Professional Practitioners
Results and Impact Keynote address on wave-in-deck loading, organised by WS Atkins. First in a series addressing key issues in Offshore Engineering. Guest audience of 150 professionals and thereafter available on the Web.
Year(s) Of Engagement Activity 2014
 
Description Offshore Structural Reliability Conference (invitation only) 
Form Of Engagement Activity A talk or presentation
Part Of Official Scheme? No
Geographic Reach International
Primary Audience Industry/Business
Results and Impact Presentation of recent advances in the description of large ocean waves and their consequences for the reliability of offshore structures
Year(s) Of Engagement Activity 2016