Wec-sim Phase 1 Validation Testing - Experimental Setup and Initial Results

In the wave energy industry, there is a need for open source numerical codes and publicly available experimental data, both of which are being addressed through the development of WEC-Sim by Sandia National Laboratories and the National Renewable Energy Laboratory (NREL). WEC-Sim is an open source code used to model wave energy converters (WECs) when subject to incident waves. In order for the WEC-Sim code to be useful, code verification and physical model validation is necessary. This paper describes the wave tank testing for the 1:33 scale experiments of a Floating Oscillating Surge Wave Energy Converter (FOSWEC). The WEC-Sim experimental data set will help to advance the wave energy converter industry by providing a free, high-quality data set for researchers and developers. This paper describes the WEC-Sim open source wave energy converter simulation tool, experimental validation plan, and presents preliminary experimental results from the FOSWEC Phase 1 testing. INTRODUCTION The nascent wave energy industry includes many young researchers and new developers who are eager to make commercialization a reality. One roadblock preventing rapid evolution of a prevailing technology is the industries tendency to avoid freely and openly sharing data. In addition, developers often need to rely on expensive numerical modelling packages and lack the resources for physical model testing data in order to validate their prototypes. WEC-Sim is an open source code, developed by Sandia and NREL, used to model wave energy converter (WEC) performance in operational and extreme waves. WEC-Sim code development is part of the US Department of Energy Wind and Water Power Technologies Office’s initiative to promote and support the emerging wave energy industry. The WEC-Sim code is a time-domain modeling tool developed in MATLAB/Simulink using the multibody dynamics solver SimMechanics [1]. WEC-Sim solves the WEC’s governing equations of motion using the Cummins time-domain impulse response formulation in 6 degrees of freedom (DOF) [2]. The WEC-Sim code has undergone verification through code-to-code comparisons; however validation of the code has been limited to publicly available experimental data sets. While these data sets provide preliminary code validation, the experimental tests were not explicitly designed for code validation, and as a result are limited in their ability to validate the full functionality of the WEC-Sim code. Dedicated physical model tests for WEC-Sim validation are being performed in two phases. This paper will provide an overview of the dedicated WEC-Sim validation experimental wave tank tests performed at the Oregon State University’s (OSU) Directional Wave Basin (DWB) at Hinsdale Wave Research Laboratory (HWRL). Phase 1 of experimental testing was focused on the FOSWEC device characterization, and was completed in winter 2015. Phase 2 will be focused on characterization of the FOSWEC’s dynamics and performance, and is scheduled for spring 2016. This phased approach allowed for initial data to be analyzed, refinements to the numerical and physical model, and evaluation of instrumentation and testing methods. The experiments have been designed explicitly to validate the performance of the WEC-Sim code and its new feature additions. Upon completion, the WEC-Sim validation data set will be made publicly available to the wave energy community, so that it can be used as a numerical benchmarking data set. For the physical model testing, a highly sophisticated and controllable model of a floating wave energy converter, the FOSWEC, has been designed and constructed. FOSWEC instrumentation includes state-of-the-art devices to measure pressure fields, motions in 6 Degrees of Freedom (DOF), multiaxial load cells, torque transducers, position transducers, and encoders. Most of the collected data has redundancy from multiple types of instrumentation. The model also incorporates a fully programmable Power Take-Off (PTO) system which can be used to generate or absorb the hydrokinetic wave energy. Proceedings of the ASME 2016 35th International Conference on Ocean, Offshore and Arctic Engineering OMAE2016 June 19-24, 2016, Busan, South Korea