| Summary: | 博士 === 國立臺灣海洋大學 === 河海工程學系 === 100 === This study investigates the performance of a piston-type porous wave energy converter (WEC), which consists of a solid wall, a vertical porous plate, a transmission bar, a rigid block constrained by rollers, a spring, and a damper. This WEC is subjected to the external dynamic loading of a wave attack. For this wave-body interaction problem, a single-degree-of-freedom (SDOF) system is developed to describe the WEC response. Linear wave theory governs the entire fluid domain. Darcy’s law and a complex porous-effect parameter are applied to the flow moving through a porous plate. The eigenfunction expansion method and the multi-domain boundary element method (MBEM) can be used to solve full and partial piston-type porous WEC cases, respectively. Examples are provided to demonstrate the added mass and the radiation damping from the wave-body interactions, the wave reflection from the WEC, the response to the wave loading, and the instantaneous mechanical power resulting from the wave.
The results demonstrate the reasonableness of the eigenfunction expansion method, the accuracy of the MBEM, and the feasibility of the complex porous-effect parameter. Furthermore, this study determines that the response cannot approach infinity in practical applications; the increased dimensionless wavenumber ( ) reduces the variations of added mass and radiation damping, and resonance has a significant effect on cases with low damping values. The relative width of the wave-absorbing chamber ( , the wave-absorbing chamber width/the wavelength of the incident wave) significantly affects the WEC performance, with a high performance in the wave-trapping condition ( ( )). Additionally, a discussion regarding the ratio of the length of a porous plate ( ) to the water depth ( ) under various values is presented as a reference for engineers.
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