Hydrodynamic Performance Study of a Fixed-Floating Asymmetric Chamber Offshore Oscillating Water Column-Wave Energy Converter

Abstract

For the design and optimization processes of Oscillating Water Column (OWC) systems, knowledge of their hydrodynamic performance behavior is essential. While there have been extensive research efforts on understanding the hydrodynamic performance behavior of fixed-floating offshore OWCs, studies focusing on quantifying the effect of applied damping over a broad range of incoming wave heights are limited. Besides, no attempt has thus far been undertaken to optimize the hydrodynamic efficiency of fixed-floating offshore OWCs using the sequential optimization procedure proposed and used in a 2D onshore OWC in the literature. This paper addresses these omissions by deeply investigating the influence of wave height, wave period, and turbine damping parameters on the hydrodynamic performance behavior of a fixed-floating offshore OWC system. To realize these objectives, a nonlinear 3D incompressible Computational Fluid Dynamics (CFD) model based on the Reynolds-Averaged Navier-Stokes (RANS) equations and the Volume of Fluid (VOF) approach was implemented in the open-source OpenFOAM® suite to numerically simulate fluid-structure interaction under regular wave conditions. The validity of this numerical model was verified using experimental measurements in the literature, where a reasonably good correlation was achieved. The results demonstrate that the aforementioned design parameters strongly affect the device’s hydrodynamic performance. It has also been shown through a sequential optimization approach that at an optimum wave period of 1.07 s, optimum wave height of 0.01948 m, and a pneumatic damping value of 0.02 m, about 87% of peak hydrodynamic efficiency is possible for the fixed-floating offshore OWC device used in the study.