EXTREME WAVE LOADING ON OFFSHORE WAVE ENERGY DEVICES USING CFD: A HIERARCHICAL TEAM APPROACH

Lead Research Organisation: University of Plymouth
Department Name: Sch of Marine Science & Engineering

Abstract

A major design consideration for offshore wave energy devices is survivability under extreme wave loading. The aim of this project is to predict loading and response of two floating wave energy devices in extreme waves using CFD (computational fluid dynamics), in which fluid viscosity, wave breaking and the full non-linearity of Navier-Stokes and continuity equations are included. Two classes of device will be considered: Pelamis (of Ocean Power Delivery Ltd.), the prototype having already successfully generated electricity into the grid, and a floating buoy device responding in heave, known as the Manchester Bobber (Manchester University), which is being tested at 1/10th scale. Both classes of device are thought to be competitive with other renewable energy sources, being economically roughly equivalent to onshore wind energy. The CFD simulations will be undertaken in three ways: by commercial codes, CFX and COMET (STAR-CD); by recent advanced surface-capturing codes; and by the novel SPH (smoothed particle hydrodynamics) method. In order to address the uncertainties in the CFD approaches, such as the accuracy of prediction and the magnitude of computer resources required, a staged hierarchical approach of increasing computer demand will be taken in: mathematical formulation (from an inviscid single fluid to a two-fluid viscous/turbulence approach); wave description (from regular periodic to focussed wave groups including NewWave); and complexity of structure (from a fixed horizontal cylinder parallel to wave crests to the six degrees of freedom of Pelamis). At each stage, numerical results will be compared with experimental data. The significance of the inviscid v. viscous formulations, wave nonlinearity, non-breaking v. breaking conditions, and the dynamic response of the body will thus be assessed for extreme conditions. Designs for survivability should thus be better evaluated. The resulting CFD methodology will also benefit analysis of extreme wave interaction with ships, other marine vehicles and structures in general. For example interaction with freak waves and the 'green' water problem have yet to be resolved.

Related Projects

Project Reference Relationship Related To Start End Award Value
EP/D077508/1 01/10/2006 31/12/2007 £89,637
EP/D077508/2 Transfer EP/D077508/1 01/01/2008 30/09/2009 £57,145
 
Description ANSYS CFX 
Organisation Ansys, Inc
Department ANSYS CFX
Country United States 
Sector Private 
PI Contribution Partner invited to research meetings.
Collaborator Contribution Partner joined steering group for research project; contribution of ANSYS CFX software licence.
Impact Research publications.
Start Year 2007
 
Description Atkins Process 
Organisation WS Atkins
Department Atkins Process Engineering
Country United Kingdom 
Sector Private 
PI Contribution Sharing research outcomes.
Collaborator Contribution Contributing to research discussions; contributing to Project steering committee.
Impact research publications.
Start Year 2007
 
Description CD-adapco 
Organisation CD-adapco
Country United States 
Sector Private 
PI Contribution Use of software; development of test cases; demonstration of software; generation of experimental data.
Collaborator Contribution provision of computational fluid dynamics software; contribution to Project steering group; attendance at project workshops
Impact research papers
Start Year 2007
 
Description Pelamis Wave Power Ltd 
Organisation Pelamis Wave Power Ltd
Country United Kingdom 
Sector Private 
PI Contribution Numerical simulation of test cases; development of CFD for wave interaction with pelamis wave energy device.
Collaborator Contribution Attendance at Project Steering meetings; contribution to research discussions.
Impact Continued collaboration, research publications.
Start Year 2007