Resonant Cavity Waveguide and Point Defects by Phononic Crystal
Date Issued
2012
Date
2012
Author(s)
Lin, Yu-Tsung
Abstract
The disruption of the periodic alignment of perfect phononic crystals was introduced to create defective mode around the crevices. This defective mode was used to confine the progressive direction of sound wave or elastic wave. Three alignments, double-L and diagonal alignments, were investigated, and the characteristics of diagonal alignment was used to explore Y-splitter and combiner. For simulation, the finite element based program COMSOL was adopted to calculate the stopband of the phononic crystals. Various defective alignment modes were created in the crystals for the analysis of the influence of these defects on wave filtering and wave transmission. For practice, a group of aluminum bars with a diameter of 6mm and air as the background was designed at a fill rate of 0.46. Phononic crystals of square lattice were used for experiment. Finally, the results from simulation and experiment were compared, we can discover that the point defects can concentrate and limit the energy in the defects, and produce the resonance effect. In the waveguide part, the diagonal alignments defects is better than the double-L. The point defects appeared continuously, and in the path of wave guide occurred continuously partial resonance effect. Thus, it can concentrate the energy and then transfer. As the result, we can improve the waveguide effect significantly.
Subjects
Phononic Crystal
Resonant Cavity
Waveguide
Type
thesis
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