RANS-VOF modelling of the Wavestar point absorber

Abstract

Numerical modelling has become commonplace in the development of offshore structures, however for dynamic systems such as Wave Energy Convertors (WECs) conventional numerical tools may not be able to capture the full range of behaviours required for engineering analysis. This is particularly problematic in extreme seas where the nonlinearities and coupled nature of these systems become important. In this work a fully nonlinear, coupled tool for simulation of WECs is produced and compare with physical measurements. Regular wave interactions with both a fixed and freely-pitching, 1:10 scale model of the Wavestar are reproduced numerically. The numerical model is shown to be capable of predicting the pressure on the float's surface and the fully coupled motion of the device. However, the results indicate that the higher-order free surface behaviour in the vicinity of the device is not being captured correctly. Finally, the numerical model is shown to cope with an extreme regular wave including large amplitude motion, full submersion and high levels of free surface distortion. The results presented suggest that the quality of the numerical reproduction does not decrease with wave steepness; however the execution time of simulations increases significantly with increased float oscillation.

Peak Forces on Wave Energy Linear Generators in Tsunami and Extreme Waves

“…In [4], wave load of breaking waves on an overtopping device was studied in a physical wave flume, and in [5], the results were reproduced with good agreement using a RANS-VOF model. In [6,7] a point-absorbing WEC with linear-elastic mooring, moving in six degrees of freedom, was modeled showing good agreement with wave tank experiments, and in reference [8], another point-absorber device was modeled both fixed and freely floating. In [9,10], RANS-VOF models are verified with physical wave tank data and the peak forces of WECs with limited stroke length were studied.…”

Wind and wave energy resource of Germany reported by ERA-Interim reanalysis data

“…In this way, will be possible to extract two energy source from a single location, being also possible to provide some effective coastal protection in some situations [6]. The North Sea seems to represent an important area for the development of the Wave Energy Converter (WECs), this being the case of the NEMOS system (Germany) [7], Wavestar (Denmark) [8] or Wave Dragon (Denmark) [9]. The SINN Power wave energy converter [10] is another system developed in Germany, being reported two ongoing commercial projects.…”

Reliability Assessment of Water Hydraulic-Drive Wave-Energy Converters

“…However, the FEA method performs the system behaviors through computer simulation and supports a flexible combination of multiple scenarios. Taking full advantage of the FEA method with computer technology can save a lot of capital and time costs on the basis of ensuring high flexibility and fidelity [23]. In the present work, the FEA method is used to establish the structural model of the fatigue critical component of a WEC.…”