Abstract
The International Energy Agency Technology Collaboration Programme for Ocean Energy Systems (OES) initiated the OES Wave Energy Conversion Modelling Task, which focused on the verification and validation of numerical models for simulating wave energy converters (WECs). The long-term goal is to assess the accuracy of and establish confidence in the use of numerical models used in design as well as power performance assessment of WECs. To establish this confidence, the authors used different existing computational modelling tools to simulate given tasks to identify uncertainties related to simulation methodologies: (i) linear potential flow methods; (ii) weakly nonlinear Froude–Krylov methods; and (iii) fully nonlinear methods (fully nonlinear potential flow and Navier–Stokes models). This article summarizes the code-to-code task and code-to-experiment task that have been performed so far in this project, with a focus on investigating the impact of different levels of nonlinearities in the numerical models. Two different WECs were studied and simulated. The first was a heaving semi-submerged sphere, where free-decay tests and both regular and irregular wave cases were investigated in a code-to-code comparison. The second case was a heaving float corresponding to a physical model tested in a wave tank. We considered radiation, diffraction, and regular wave cases and compared quantities, such as the WEC motion, power output and hydrodynamic loading.
Highlights
The development of wave energy converters (WECs) relies on numerical simulations to optimize and evaluate their designs and provide the power performance estimates that feed into the levelized cost of energy (LCOE)
We must ask the question: how well can these devices still be modelled with standard linear tools? the power take-off (PTO) mechanisms and any control strategies are typically not included “off the shelf” in the commercial packages, spurring the development of dedicated wave energy tools based on linearized potential flow theory (e.g., WEC-Sim [6] and InWave [7])
The main result of the study is the similarity of results of using linear, weakly nonlinear and fully nonlinear models in small and medium wave conditions
Summary
The development of wave energy converters (WECs) relies on numerical simulations to optimize and evaluate their designs and provide the power performance estimates that feed into the levelized cost of energy (LCOE). There is a need for solid verification and validation of numerical codes used in wave energy applications, with regard to both how the overall level of fidelity depends on the hydrodynamic model, and how different choices within each sub-category affect the accuracy and reliability of the computed results. Other questions not yet fully answered are how the choices of fidelity levels within subsystems, such as the PTO [12] and the mooring system [13], influence the results, as well as how the inclusion of control strategies affects the reliability of the simulations Investigation of these questions is the aim of the Ocean Energy Systems (OES) wave energy conversion modelling task on the verification and validation of simulation tools for wave energy systems. Complimentary work is being undertaken in the Collaborative Computational Project in Wave Structure Interaction [22], in which members from the wider wave structure interaction community have been participating in blind comparative studies involving the interaction of focused wave events with various surface-piercing structures
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