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dc.contributor.supervisorGreaves, Deborah
dc.contributor.authorRansley, Edward Jack
dc.contributor.otherFaculty of Science and Engineeringen_US
dc.date.accessioned2015-07-30T12:55:12Z
dc.date.available2015-07-30T12:55:12Z
dc.date.issued2015
dc.date.issued2015
dc.identifier10306429en_US
dc.identifier.urihttp://hdl.handle.net/10026.1/3503
dc.descriptionFull version unavailable due to 3rd party copyright restrictions.
dc.description.abstract

This thesis discusses the development of a Numerical Wave Tank (NWT) capable of describing the coupled behaviour of Wave Energy Converters (WECs) and their moorings under extreme wave loading. The NWT utilises the open-source Computational Fluid Dynamics (CFD) software OpenFOAM(R) to solve the fully nonlinear, incompressible, Reynolds-Averaged Navier-Stokes (RANS) equations for air and water using the Finite Volume Method (FVM) and a Volume of Fluid (VOF) treatment of the interface. A method for numerically generating extreme waves is devised, based on the dispersively-focused NewWave theory and using the additional toolbox waves2Foam. A parametric study of the required mesh resolution shows that steeper waves require finer grids for mesh independence. Surface elevation results for wave-only cases closely match those from experiments, although an improved definition of the flow properties is required to generate very steep focused waves. Predictions of extreme wave run-up and pressure on the front of a fixed truncated cylinder compare well with physical measurements; the numerical solution successfully predicts the secondary loading cycle associated with the nonlinear ringing effect and shows a nonlinear relationship between incident crest height and horizontal load. With near perfect agreement during an extreme wave event, the reproduction of the six degree of freedom (6DOF) motion and load in the linearly-elastic mooring of a hemispherical-bottomed buoy significantly improves on similar studies from the literature.

Uniquely, this study compares simulations of two existing WEC designs with scale-model tank tests. For the Wavestar machine, a point-absorber constrained to pitch motion only, results show good agreement with physical measurements of pressure, force and float motion in regular waves, although the solution in the wake region requires improvement. Adding bespoke functionality, a point-absorber designed by Seabased AB, consisting of a moored float and Power Take-Off (PTO) with limited stroke length, translator and endstop, is modelled in large regular waves. This represents a level of complexity not previously attempted in CFD and the 6DOF float motion and load in the mooring compare well with experiments.

In conclusion, the computational tool developed here is capable of reliably predicting the behaviour of WEC systems during extreme wave events and, with some additional parameterisation, could be used to assess the survivability of WEC systems at full-scale before going to the expense of deployment at sea.

en_US
dc.description.sponsorshipEngineering and Physical Sciences Research Council (EPSRC) via SuperGen UK Centre for Marine Energy Research (UKCMER)en_US
dc.language.isoenen_US
dc.publisherPlymouth Universityen_US
dc.subjectComputational Fluid Dynamics (CFD)
dc.subjectCFD, Computational Fluid Dynamicsen_US
dc.subjectOpenFOAMen_US
dc.subjectSurvivabilityen_US
dc.subjectWave Energy Converteren_US
dc.subjectRANSen_US
dc.subjectVOFen_US
dc.subjectExtreme wavesen_US
dc.titleSurvivability of Wave Energy Converter and Mooring Coupled System using CFDen_US
dc.typeThesisen_US
plymouth.versionEdited versionen_US
dc.identifier.doihttp://dx.doi.org/10.24382/1289


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