تحليل يك ساختار بهينه فراماده به منظور افزايش پهناي شكاف و برداشت انرژي از امواج آكوستيكي با استفاده از وصله‌ي پيزوالكتريك

In the contemporary context of the expansion of the manufacture of small, low-power electrical equipment an‎d the optimal use of renewable energies, there has been an intensification of focus on the development of a functional power source to substitute for batteries. The objective of this initiative is to facilitate the provision of electrical energy to the aforementioned devices. A potential solution to this problem is the utilisation of the energy present within the acoustic waves of the environment to supply electrical power to low-power equipment. As is known, in general, the absorption density of acoustic waves is very low. Consequently, in the process of transforming acoustic energy into electrical energy, it is imperative to initially concentrate ambient sound waves through conventional methodologies, an‎d then to optimise the electrical energy harvested by a compatible harvester. The deployment of Helmholtz chambers, in conjunction with the fabrication an‎d design of metamaterials, constitutes a range of techniques aimed at enhancing the concentration of ambient sound waves within a given environment. This thesis presents an analysis an‎d investigation of an optimal metamaterial structure to increase energy harvesting from acoustic waves in a specific frequency range of 3000-5000 Hz using a piezoelectric patch, as well as the effect of that structure on the acoustic ban‎dgap. For the first time, non-cylindrical crystals with a rhombic-square arrangement have been utilised to enhance the focusing of acoustic waves. The effect of concentrated mass added to the top of the crystals on the acoustic ban‎dgap, an‎d the effect of changing the angle of incidence of the sound source on the amount of energy harvested at the inclusion site, have also been investigated. The system modelling was performed in the 3D environment of COMSOL software, version 6. The selec‎tion of optimal parameters was achieved through the implementation of two distinct algorithms: the artificial neural network algorithm an‎d the genetic algorithm. These algorithms were employed in conjunction with the established link between the MATLAB an‎d COMSOL software environments. The following parameters were considered in the optimization process in order to selec‎t optimal values: crystal length, crystal radius, crystal curvature radius, centre-to-centre distance an‎d metamaterial plate thickness. Moreover, the relationships governing the energy harvesting problem, ban‎dgap, an‎d sound transmission loss are presented. These relationships are based on Bloch theory. The results demonstrated that employing a metamaterial comprising hyperbolic crystals of optimised dimensions in comparison to a metamaterial incorporating a cylindrical crystal under equivalent environmental conditions an‎d mass yielded a considerably elevated mean energy harvest within a designated frequency range of 3000-5000 Hz. Also, comparing the acoustic ban‎dgap an‎d sound transmission loss range results for the two metamaterials reveals that the metamaterial with a hyperbolic crystal has a larger acoustic ban‎dgap than the metamaterial with a cylindrical crystal, due to the increased mechanical impedance. However, adding concentrated mass to the hyperbolic crystal resulted in a larger calculated ban‎dgap compared to the previous two cases. Changing the angle of radiation also showed that the best energy harvesting is possible in vertical radiation mode, followed by horizontal radiation. Finally, the simulation results were compared an‎d validated against the experimental results for both the energy harvesting an‎d the ban‎dgap cases. Experimental results were obtained an‎d compared for two metamaterial cases featuring a square-rhombic arrangement: one with a hyperbolic crystal an‎d the other with a cylindrical crystal.

سعيد ضيائي راد , علي لقماني

حسن نحوي , رضا تيكني , روح اله طالبي توتي