CFD solutions for the floating offshore structures in OpenFOAM®

This dissertation focuses on a Computational Fluid Dynamics (CFD) study of offshore floating structures, particularly floating Wave Energy Converter (WEC) devices. The open-source CFD software, OpenFOAM®, is evaluated for its effectiveness in simulating relevant phenomena. The study presents the hydrodynamic analysis and optimization of a novel axisymmetric single cylindrical WEC equipped with a moonpool, called MoonWEC. The primary aim is to optimize the design of a small-scale model of the MoonWEC device by minimizing pitch rotations, enhancing heave motion, and facilitating its moonpool oscillations using CFD. A set of new laboratory experiments was conducted to characterize the hydrodynamic response of the device. These experiments were numerically reproduced in OpenFOAM. A detailed explanation of the numerical setup in OpenFOAM is provided in the thesis for the readers to reproduce the CFD model for any moored floating structure. The heave and pitch responses were analyzed by comparing experimental and numerical data, showing good agreement. The results showed that the MoonWEC device can achieve the preferred excitation in heave, but it can also undergo the unpreferred excitation in pitch. By shifting the centre of mass, MoonWEC was numerically optimized to reduce the pitch rotations without affecting the heave oscillations. The moonpool motion was also analyzed for the optimized small-scale model. The study concludes that the CFD model in OpenFOAM, coupled with the MooDy library, can accurately simulate the hydrodynamics of the MoonWEC. The optimization study shows that the centre of mass of the device is a key parameter in controlling the natural period of the device in pitch. The analysis of the moonpool shows that the MoonWEC has the potential to generate significant power. This research contributes to the ongoing efforts to develop wave energy as a sustainable and renewable energy source.