Numerical investigation of wave structure interaction with application to wave energy devices

Abstract

Wave energy has become one of the most promising energy resources and hence has attracted more attention from the governments and energy companies. In order to meet the growing demands on global energy, the next generation of energy extracting device needs to be more efficient with less operation cost, and as an offshore structure, the survivability also needs to be taken into consideration. Therefore, it is vital that the hydrodynamic behaviour of the energy device can be predicted accurately at the initial design stage.

In this research, the wave structure interaction with application to wave energy device is studied numerically through an open source CFD library: OpenFOAM. The computational fluid dynamic (CFD) analysis based on the Reynolds Average Navier Stokes (RANS) equations is used to investigate the interaction between wave and structure, and array effects among devices. The numerical method with a reasonable computational cost can be an alternative to physical experimental test in offshore engineering. The background to this research is firstly introduced, including methodologies adopted in this study, followed by a series of case study to demonstrate the applicability of the numerical model. These include wave generation validation, hydrodynamic behaviour determination, and the predication of the performance of wave point absorber and wave point absorbers array.

It has been shown that the numerical model is capable of modelling wave propagation and interaction with structure including nonlinear effect with a reasonable degree of accuracy. The wave point absorber energy device has been chosen as the object to study. The RANS approach in time domain improves the accuracy when compared with the potential theory based method. The influence of wave point absorber devices array on their performance is then investigated under the irregular wave conditions in order to improve the overall performance. The influence factors include array configuration, separation distance and wave direction.
The study yields an improved understanding of wave-structure problem and has extended the range of RANS model used in wave energy research.

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