Wave Energy Converter Based On Helmholtz Mode

Saadat, Yalda
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[Honolulu] : [University of Hawaii at Manoa], [December 2013]
The present study examines a new means of wave energy conversion inspired by geological toilet bowls and blowholes in nature that are able to concentrate ocean wave energy in a basin. The intention of this project is to experimentally investigate the geometry of toilet bowls in a wave tank enclosing the size of the basin and the channel in order to attract Helmholtz resonance and introduce a new device that is called resonator. The device includes a basin with a horizontal cross-sectional area at the level of meanwater level A0 connected to the incoming waves by a narrow channel of width B and Length L, where the maximum water depth is H. The geometry of the device that is scaled by Froude number, causes an oscillating fluid within the channel with a Helmholtz frequency of σ2H=gHB/A0L. In this article, the relation of the aforementioned frequency to the device's geometry is examined in both 1/25th and 1/7th scaled models. Additionally, the effect of the device's length and the angle of the device's winglets at the inlet of the channel are explored. Lastly, in this article, the 1/25th device is tested with a two-dimensional particle image velocimetry instrument (PIV) to determine the instantaneous velocity field through the scaled model. The experiments demonstrate that reducing the winglets' angle results in less high order harmonics, therefore, higher performance of wave energy absorption. In addition, the alignment of the axis of the resonator to incoming waves plays an important role in increasing the efficiency of the device. Moreover, the collected data determines that resonance in the channel results in an amplification of wave height and corresponding wave power absorption relative to incoming waves. Accordingly, the appropriate location for placing the power take-off (PTO) can be empirically determined. There are different operating points for power extraction at different mean velocity in the channel, in which, the efficiency of the PTO as well as the wave power ratio flux in the channel are changing. Therefore, PTO can be tuned to operate at optimum power point. This thesis that is the beginning of my journey, is dedicated to all people in my country and in the world with the same abilities and desires as me, who would like to study and enjoy expressing themselves in academia, but, are banned from doing so because of their beliefs, their religions, their thoughts and their way of thinking.
M.S. University of Hawaii at Manoa 2013.
Includes bibliographical references.
wave energy conversion
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