Application of Coupled Numerical Simulation to Design Wave Energy Converters

Connolly, Aengus John (Wood Group) | Brewster, Paul (Pure Marine Gen)

OnePetro 

ABSTRACT

This paper describes a time domain numerical simulation methodology, based on a coupled analysis technique, which may be used to model wave energy converters. Linear hydrodynamic forces based on radiation-diffraction theory are combined with a non-linear finite element structural analysis technique. Results from the numerical simulations are validated by comparison with experimental data derived from model-scale tank test facilities. Data obtained from the empirical tests combined with the numerical simulations, is helping to optimise the design of a highly innovative wave energy device, with a view to further improving the highly promising performance metrics already demonstrated by it.

INTRODUCTION

While wind and solar energy systems have already seen widespread deployment, wave energy devices have struggled to achieve the required technical and commercial readiness levels. Apart from the obvious engineering design challenges, another key issue is the availability of suitable simulation packages. Industry requires software tools which facilitate modelling of the applied loads and associated structural response in full complexity, through relevant descriptions of the coupling between the structural and hydrodynamic models. Detailed numerical simulation capabilities allow wave energy device developers to gain a deeper understanding of the energy generation potential of their device. Information derived from realistic engineering simulations facilitates progressive migration through the various design stages, from conceptual, scale models, prototypes, through to full scale versions.

This paper describes a time domain numerical simulation methodology, based on a coupled analysis technique, which may be used to model wave energy converters (WECs). Fluid forces on the floating body are based on potential flow theory, including incident, diffraction and radiation potentials. Hydrodynamic coupling between adjacent bodies, a key facet of the validation programme, and viscous damping is also considered. Structural analysis of the mooring lines and mechanical linkages is performed accurately using an industry-proven finite element formulation, which is based on a hybrid beam element with fully coupled axial, bending and torque forces. Power take-off (PTO) is simulated using a combination of spring and damper elements in the numerical solver, presenting the designer with key information regarding power output and energy generation potential.