Thesis (MScEng)--University of Stellenbosch, 2008. / Bibliography. Also available via the Internet.

 As fossil energy is depleting and global warming effect is worsening rapidly, developing renewable energies becomes the top priority in most countries. In recent years, wave energy has attracted more and more attention due to its high energy density and enormous global capacity. The goal of this study is to carry out a numerical study of the hydrodynamic performance of a point-absorbing wave energy converter. In this study, an accurate and efficient numerical wave fume was established first. Commercial software code FLUENT?, which is a state-of-the-art computer program package for modeling fluid flow and heat transfer, was used for the numerical simulation. Based on the Navier-Stokes equations for viscous, incompressible fluid and Volume of fluid (VOF) method, a numerical wave tank was developed. Dynamic meshing method was used to simulate the wavemaker, and Geo-Reconstruct scheme was used to capture and reconstruct the free surface. A wave-absorbing method employing porous medium model was proposed to act as the wave absorbing beach, which can absorb the wave energy efficiently. A series of regular waves were simulated using the proposed numerical method. Validation has been made by physical experiments. After developing the wave flume model, a cylinder, which represents the point-absorbing wave energy converter (WEC), was added into the wave flume. The hydrodynamic behavior of the WEC was studied. The numerical results were also compared with physical experiments. Based on the numerical simulation results, suggestions on optimizing the point-absorber are provided. In this study, eight wave cases, with different wave period and wave length were simulated. The results show that the numerical simulation can match well with the physical wave tank result. Both the wave height and wave period in different cases can match well between the numerical simulation and physical wave tank results. In the wave-cylinder simulation, the results also show a good match in the numerical study and physical study. This numerical model is very significant in ocean structure design. The cylinder tested in this study can be easily changed to a ship or an offshore-platform. Compared with the physical experiment, numerical simulation is more flexible. The simulation can be carried on a large time span and spatial scale. The geometry can be changed easily. Also the cost of numerical simulation is relatively cheap compared with the physical experiment. / published_or_final_version / Mechanical Engineering / Master / Master of Philosophy

Graduation date: 1997

A numerical method is described to study directional wave effects on large offshore structures of arbitrary shape, based on an extension of linear diffraction wave theory for regular waves. A computer program has been developed to compute loading transfer functions and response amplitude operators and hence the loading and response spectra for both long- and short-crested random waves. Cosine powered directional spreading functions which are independent of frequency have been used to account for the shortcrestedness of waves. Comparisions of the results for long- and short-crested seas show that there is a significant reduction in the loading, and hence in the response, due to shortcrestedness of waves. The probabilistic properties of the components of the loading and response are described. Since the sea surface is assumed to follow a Gaussian distribution, these are also random Gaussian variables. In short-crested waves, the loading and response components occur both in-line and transverse to the principal wave direction. Thus the maximum horizontal loading and response may occur in an arbitrary horizontal direction. An analytical method is developed to describe also the probabilistic properties of the maxima of the components and the maxima of their horizontal resultants. In the present study, results are described for a freely floating box. Comparisons are made with published results and are found to be quite favourable. / Applied Science, Faculty of / Civil Engineering, Department of / Graduate

Thesis (M.A.)--Oregon State University, 2009. / Printout. Includes bibliographical references (leaves 164-169). Also available on the World Wide Web.

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