scholarly journals Targeted band gap creation using mixed sonic crystal arrays including resonators and rigid scatterers

2007 ◽  
Vol 90 (24) ◽  
pp. 244104 ◽  
Author(s):  
E. Fuster-Garcia ◽  
V. Romero-García ◽  
J. V. Sánchez-Pérez ◽  
L. M. García-Raffi
Keyword(s):  
Band Gap ◽  
Sonic Crystal ◽  
Gap Creation

Parametric Study on Rectangular Sonic Crystal

2012 ◽  
Vol 152-154 ◽  
pp. 281-286 ◽  
Author(s):  
Arpan Gupta ◽  
Kian Meng Lim ◽  
Chye Heng Chew
Keyword(s):  
Band Gap ◽  
Periodic Structure ◽  
Parametric Study ◽  
Sound Propagation ◽  
Periodic Structures ◽  
Sound Attenuation ◽  
Experimental Results ◽  
Center Frequency ◽  
Sonic Crystal ◽  
Sonic Crystals

Sonic crystals are periodic structures made of sound hard scatterers which attenuate sound in a range of frequencies. For an infinite periodic structure, this range of frequencies is known as band gap, and is determined by the geometric arrangement of the scatterers. In this paper, a parametric study on rectangular sonic crystal is presented. It is found that geometric spacing between the scatterers in the direction of sound propagation affects the center frequency of the band gap. Reducing the geometric spacing between the scatterers in the direction perpendicular to the sound propagation helps in better sound attenuation. Such rectangular arrangement of scatterers gives better sound attenuation than the regular square arrangement of scatterers. The model for parametric study is also supported by some experimental results.

scholarly journals ACOUSTIC BAND GAP FORMATION IN METAMATERIALS

2010 ◽  
Vol 24 (25n26) ◽  
pp. 4935-4945 ◽  
Author(s):  
D. P. ELFORD ◽  
L. CHALMERS ◽  
F. KUSMARTSEV ◽  
G. M. SWALLOWE
Keyword(s):  
Band Gap ◽  
Lattice Constant ◽  
Low Frequency ◽  
Band Gaps ◽  
Gap Formation ◽  
Individual Band ◽  
Resonance Band ◽  
Frequency Regime ◽  
Sonic Crystal ◽  
The Individual

We present several new classes of metamaterials and/or locally resonant sonic crystal that are comprised of complex resonators. The proposed systems consist of multiple resonating inclusion that correspond to different excitation frequencies. This causes the formation of multiple overlapped resonance band gaps. We demonstrate theoretically and experimentally that the individual band gaps achieved, span a far greater range (≈ 2kHz) than previously reported cases. The position and width of the band gap is independent of the crystal's lattice constant and forms in the low frequency regime significantly below the conventional Bragg band gap. The broad envelope of individual resonance band gaps is attractive for sound proofing applications and furthermore the devices can be tailored to attenuate lower or higher frequency ranges, i.e., from seismic to ultrasonic.

Numerical Studies on Band-Gap Structures and Resonant-Mode Wave-Guides of Typical Sonic Crystals Made of Rigid Cylinders in Fluid by Means of Elastic FDTD Method

2005 ◽  
Author(s):  
Toyokatsu Miyashita
Keyword(s):  
Band Gap ◽  
Fdtd Method ◽  
Transmission Band ◽  
Resonant Mode ◽  
Mode Wave ◽  
Periodic Arrays ◽  
Sonic Crystal ◽  
Wave Guides ◽  
Periodic Repetition ◽  
Fdtd Methods

We have investigated band-gap structures of three typical sonic/phononic crystals, namely periodic arrays of methacrylic resin cylinders in air, aluminum cylinders in air, and steel cylinders in water, by two different FDTD methods; one method is a sonic one that deals with only longitudinal waves, and the other is an elastic one that includes also shear waves. We show that both FDTD methods give almost the same band-gap structures for the former two crystals. Namely, the band-gaps by the sonic FDTD method lie at higher frequency only by 0.01 ~ 0.02 in the normalized frequency than those by the elastic one. The theoretical band-gap structures agree well with the experimental ones. In contrast, it is shown that the third crystal should be analyzed by the elastic FDTD method. Resonant-mode wave-guides are made by a periodic repetition of single-defects along a line in a sonic crystal of rigid cylinders in air. The obtained resonant and well-guided transmission band lies inside the full band-gap of the original bulk crystal. A combination of such wave-guides with a line-defect wave-guide is shown to have desirable characteristics for filtered wave-guides and wave-couplers.

ELECTRONIC STRUCTURE OF GRAPHENE NANORIBBONS SUBJECTED TO TWIST AND NONUNIFORM STRAIN

2011 ◽  
Vol 20 (01) ◽  
pp. 153-160 ◽  
Author(s):  
A. DOBRINSKY ◽  
A. SADRZADEH ◽  
B. I. YAKOBSON ◽  
J. XU
Keyword(s):  
Band Gap ◽  
Density Functional ◽  
Graphene Nanoribbons ◽  
Tight Binding ◽  
Tight Binding Approximation ◽  
Functional Theory ◽  
Gap Opening ◽  
Gap Creation ◽  
Band Gap Modulation ◽  
Twisted Graphene

Graphene nanoribbons exhibit band gap modulation when subjected to strain. While band gap creation has been theoretically investigated for uniaxial strains, other deformations such as nanoribbon twist have not been considered. Our main objective in this paper is to explore band gap opening in twisted graphene nanoribbons that have metallic properties under tight-binding approximation. While simple considerations based on the Hückel model allow to conclude that zigzag graphene nanoribbons exhibit no band gap when subjected to twist, the Hückel model overall may be inaccurate for band gap prediction in metallic nanoribbons. We utilize Density Functional Theory Tight-Binding Approximation together with a requirement that energy of twisted nanoribbons is minimized to evaluate band gap of metalic armchair nanoribbons. Besides considering twisting deformations, we also explore the possibility of creating band gap when graphene nanoribbons are subject to inhomogeneous deformation such as sinusoidal deformations.

Perforation-rotation based approach for band gap creation and enlargement in low porosity architected materials

2020 ◽  
Vol 245 ◽  
pp. 112331
Author(s):  
Xiangyu Tian ◽  
Wenjiong Chen ◽  
Renjing Gao ◽  
Shutian Liu ◽  
Jiaxing Wang
Keyword(s):  
Band Gap ◽  
Gap Creation ◽  
Low Porosity

ACOUSTIC BAND GAP FORMATION IN TWO-DIMENSIONAL LOCALLY RESONANT SONIC CRYSTALS COMPRISED OF HELMHOLTZ RESONATORS

2009 ◽  
Vol 23 (20n21) ◽  
pp. 4234-4243 ◽  
Author(s):  
L. CHALMERS ◽  
D. P. ELFORD ◽  
F. V. KUSMARTSEV ◽  
G. M. SWALLOWE
Keyword(s):  
Band Gap ◽  
Experimental Testing ◽  
Wide Band ◽  
Band Gaps ◽  
Gap Formation ◽  
Helmholtz Resonators ◽  
Multiple Resonance ◽  
Resonance Band ◽  
Sonic Crystal ◽  
Sonic Crystals

We present a new type of sonic crystal technology offering a novel method of achieving broad acoustic band gaps. The proposed design of a locally resonating sonic crystal (LRSC) is constructed from "C"-shaped Helmholtz resonators as opposed to traditional solid scattering units. This unique construction enables a two band gap system to be generated in which the first — a Bragg type band gap, arises due to the periodic nature of the crystal, whilst the second gap results from resonance of the air column within the resonators. The position of this secondary band gap is found to be dependent upon the dimensions of the resonating cavity. The band gap formation is investigated theoretically using finite element methods, and confirmed through experimental testing. It is noted that the resonance band gaps detected cover a much broader frequency range (in the order of kHz) than has been achieved to date. In addition the possibility of overlapping such a wide band gap with the characteristic Bragg gap generated by the structure itself could yield gaps of even greater range. A design of sonic crystal is proposed, that comprises of several resonators with differing cavity sizes. Such a structure generates multiple resonance gaps corresponding to the various resonator sizes, which may be overlapped to form yet larger band gaps. This multiple resonance gap system can occur in two configurations. Firstly a simple mixed array can be created by alternating resonator sizes in the array and secondly using a system coined the Matryoshka (Russian doll) array in which the resonators are distributed inside one another. The proposed designs of LRSC's offer a real potential for acoustic shielding using sonic crystals, as both the size and position of the band gaps generated can be controlled. This is an application which has been suggested and investigated for several years with little progress. Furthermore the frequency region attenuated by resonance is unrelated to the crystals lattice constant, providing yet more flexibility in the design of such devices.

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