The eventual deployment of wave energy converters (WECs) on a commercial scale will necessitate the grouping of devices into arrays or "wave farms," in order to minimize overhead costs of mooring, maintenance, installation, and electrical cabling for shoreward power delivery. Closely spaced WECs will interact hydrodynamically through diffracted and radiated waves. Recent research has focused on the WEC wave field and used its structures to design constructive WEC arrays as well as to describe the means of WEC energy absorption. In this study, the WEC wave field is investigated for a single WEC and a five WEC array with linear wave theory and experimental results. Both regular waves and spectral seas are considered. Computational results are produced with the linear boundary-element-method (BEM) hydrodynamic software WAMIT for a simple WEC geometry. Experimental data comes from WEC array tests that took place at Oregon State University over the winter of 2010-11 [1]. The experimental measurements help validate the computational modeling, and the computational models serve as an aid to interpreting the experimental data.
Results reveal two universal WEC wave field features - partially standing waves and a wave shadow, both of which are the result of the coherent interaction of the planar incident wave with the circular generated wave, composed of
the diffracted and radiated waves. The partial standing waves in the offshore are seen qualitatively in experimental data but could not be exactly reproduced computationally, because the computational model is only a simple representation of the physical model. In the lee of the WEC, the measured longshore structure of the wave shadow is in good agreement with theoretical expectations as well as computational results. It is believed that the agreement is
because the formation of the wave shadow is dominated by energy extraction, which was approximately the same for both the computational and physical models.
A study of the linear WEC wave field in regular waves and spectral seas reveals patterns such as the wave shadow that have also been found in experimental data. The positions and magnitudes of the offshore partially standing
waves are very sensitive to wavelength, and WEC geometry, motions and location, and in spectral seas, they are smoothed when considering significant wave height. All of which suggest that it may be difficult to use them advantageously in the design of WEC arrays. The wave shadow is a dominant feature of the WEC wave field for both regular waves and spectral seas. It appears to be fairly generic and to be based on power absorption. In the
design of WEC arrays, rather than attempting constructive interference by using standing wave crests, perhaps the best one can do is to avoid destructive interference of the wave shadow. / Graduation date: 2013
| Identifer | oai:union.ndltd.org:ORGSU/oai:ir.library.oregonstate.edu:1957/33939 |
| Date | 01 August 2012 |
| Creators | McNatt, J. Cameron |
| Contributors | Ozkan-Haller, H. Tuba |
| Source Sets | Oregon State University |
| Language | en_US |
| Detected Language | English |
| Type | Thesis/Dissertation |
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