Session: 09-02-01 Wave Energy: Hydrodynamics 1

Paper Number: 123824

123824 - Hydrodynamic Analysis of Different Configurations of the M4 Wave Energy Converter System Using Oregen. 

Over the past decade, the Moored, Multi-float, and Multi-Mode (M4) wave energy converter has been widely studied with the aim capacity O(MW) at full scale. The devices have a single bow float and one or more mid floats in rigid connection. Stern floats are connected by a beam to the mid floats with a hinge above the mid float with damper for power conversion. A system with say two mid floats and two stern floats would be termed 122.  These have been based on self-alignment with the wave direction from a single point mooring due to wave drift effects. This requires small ocean currents which is often the case, but tidal currents are generally significant on continental shelfs affecting alignment and here we consider configurations which are insensitive to wave direction by having hinge axes and associated beams at 90 degrees. This magnifies the number of cases for consideration. In this paper, we present a frequency domain hydrodynamic response prediction program OREGEN-BEM developed for multi-body systems, based on the boundary element method (BEM) with the OpenMP algorithm for efficiency. It is applied to analyze the dynamic response of various M4 systems with kinematic and mechanical constraints, including existing 111, 121, 122, and 132 configurations. The algebraic equations corresponding to the clamped connection between body-to-body due to the beam structure and revolution joint connection are analytically derived, and they are coupled with the system equation through the Lagrangian multiplier method. In this paper, a comprehensive validation study for these four configurations is conducted to compare the numerical results from commercial software Wamit, Wadam, and OrcaWave and the experiment data. The comparison results demonstrate the results obtained by the OREGEN are accurate and reliable, and the computational speed is fast due to its implementation of a parallel algorithm. Results for some omni-directional configurations with hinges at right angles will also be presented. The frequency domain method is highly efficient and suitable for multi-float configuration assessment in the offshore renewable energy field.

Presenting Author: Peter Stansby University of Manchester

Presenting Author Biography: Peter Stansby has been Professor of Hydrodynamics at Manchester University since 1990.

He obtained his BA in Engineering and his PhD in Aerodynamics at Cambridge University. He then worked for Atkins Research and Development near London on wind and offshore engineering for two years. On moving to Manchester University in 1980, his early research interests were in wave and current loading on offshore structures, specializing in vortex-induced vibrations. Since around 1990 he has worked on coastal hydrodynamics, mainly in relation to shallow-water flows and surf zone waves.

Since 2000 he has been involved with the Tyndall Centre on the Coastal programme. He now leads the Coastal Flooding component of the EPSRC/EA programme Flood Risk Management Research Consortium (FRMRC2). Since 2004 he has become involved with wave energy devices, developing a particular robust point absorber, the Manchester Bobber, supported by the Carbon Trust and six industrial partners. His research on renewable energy now extends to marine current turbines, funded by EdF and ETI, and offshore wind turbines, funded by Garrad Hassan. The University of Manchester has recently become a partner in the Energy Technology Institute for work on marine current turbines. Since 2005 he has become active in the novel numerical method SPH (smoothed particle hydrodynamics) which shows great promise for violent surface flows.

He has been an investigator on over 30 grants and contracts, mainly from EPSRC. He has been an associate editor for the ASCE Journal of Hydraulic Engineering and on the editorial board of Applied Ocean Research. He is a Fellow of the Royal Academy of Engineering and the Institution of Civil Engineers. He has published over 80 papers in international refereed journals.

Authors:

Gangqiang Li University of Manchester
Peter Stansby University of Manchester