2d And 3d Acoustic Metamaterials Using Space Coil Design
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2d And 3d Acoustic Metamaterials Using Space Coil Design Santosh K. Maurya1, Manu Sahay1, Shobha Shukla1, Sumit Saxena1 1 Nanostructure Engineering and Modeling Laboratory Department of Metallurgical Engineering and Materials Science Indian Institute of Technology Bombay Mumbai, 400076
ABSTRACT Various promising applications such as acoustic cloaking, sub-wavelength imaging, acoustic wave manipulation, transmission or reflection control etc. are feasible because of the ability of manipulating sounds and vibrations using artificially engineered “Acoustics metamaterials”. Recent works on space-coiling acoustic metamaterials show their extreme constitutive parameters like large refractive index, double negativity and zero mass density. Three dimensional structures have a wide application in sub-wavelength broadband acoustic wave suppression due to huge attenuation. Here we report the study of propagated and transmitted wave through 3D acoustic metamaterials structure using finite element method. Our simulations on 3D structure show a huge absorption/damping over few hundreds kilohertz frequency range. INTRODUCTION Various promising applications such as acoustic cloaking [1], sub-wavelength focusing [2-8], surface wave manipulation, extraordinary transmission [9-11] or reflection control, transformation acoustics, etc. are feasible because of the ability of manipulating sound waves [10] and vibrations using artificially engineered “Acoustics meta-materials”. However, achieving negative acoustic parameters (negative bulk modulus (B) and negative rho (ρ)) is still a challenge and requires a deep understanding. Recently, Zixian Liang et al have demonstrated the use of a space coiling structure [12] for constructing a phononic crystal [13] with band folding at low frequencies. Simulation studies have suggested that a space coiling structure helps in increasing the path length of acoustic wave which not only leads to the enhancement of refractive index [12] but also changes the other constitutive parameters like bulk modulus (B), refractive index (n) and mass density (ρ). Further, their studies have shown that a 2D wedge shaped arrangement of the unit cells with space-coiling structures demonstrates negative refractive index and density near zero. Yangbo Xie et al have experimentally demonstrated the broadband negative index using space coiling structures [14]. The conditions were slightly modified from the previous work like the height of the space-coiling unit cell and material (thermoplastic instead of Brass). Their work has suggested that the change in the number of maze and the dimensions can make the broadband negative index tunable. Tobias Frenzel et al have experimentally reported the first 3D labyrinthine metamaterials [15]. Their studies have suggested that such structures can
achieve positive phase and slower group velocities of sound over a large range of relevant acoustic frequencies. EXPERIMENT Here in, we have attempted to study the propagation of acoustic waves in space coiled 3D labyrinthine structures [1
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