scholarly journals Angular Band Gaps in Sonic Crystals: Evanescent Waves and Spatial Complex Dispersion Relation

2013 ◽  
Vol 135 (4) ◽  
Author(s):  
V. Romero-García ◽  
R. Picó ◽  
A. Cebrecos ◽  
K. Staliunas ◽  
V. J. Sánchez-Morcillo
Keyword(s):  
Dispersion Relation ◽  
Spatial Dispersion ◽  
Evanescent Waves ◽  
Phononic Crystals ◽  
Band Gaps ◽  
Fluid Medium ◽  
Longitudinal Modes ◽  
Periodic Distribution ◽  
Numerical Predictions ◽  
Sonic Crystals

Phononic crystals are artificial materials made of a periodic distribution of solid scatterers embedded into a solid host medium with different physical properties. An interesting case of phononic crystals, known as sonic crystals (SCs), appears when the solid scatterers are periodically embedded in a fluid medium. In SCs only longitudinal modes are allowed to propagate and both the theoretical and the experimental studies of the properties of the system are simplified without loss of generality. The most celebrated property of these systems is perhaps the existence of spectral band gaps. However, the periodicity of the system can also affect to the spatial dispersion, making possible the control of the diffraction inside these structures. In this work we study the main features of the spatial dispersion in SCs from a novel point of view taking into account the evanescent properties of the system, i.e., studying the complex spatial dispersion relations. The evanescent behavior of the propagation of waves in the angular band gaps are theoretically and experimentally observed in this work. Both the numerical predictions and the experimental results show the presence of angular band gaps in good agreement with the complex spatial dispersion relation. The results shown in this work are independent of the spatial scale of the structure, and in principle the fundamental role of the evanescent waves could be also expected in micro- or nanoscale phononic crystals.

scholarly journals “Fuzzy Band Gaps”: A Physically Motivated Indicator of Bloch Wave Evanescence in Phononic Systems

Crystals ◽  
2021 ◽  
Vol 11 (1) ◽  
pp. 66
Author(s):  
Connor D. Pierce ◽  
Kathryn H. Matlack
Keyword(s):  
Wave Propagation ◽  
Dispersion Relation ◽  
Quantitative Measure ◽  
Bloch Wave ◽  
Phononic Crystals ◽  
Wave Transmission ◽  
Band Gaps ◽  
Dissipative Systems ◽  
Frequency Range ◽  
Wave Modes

Phononic crystals (PCs) have been widely reported to exhibit band gaps, which for non-dissipative systems are well defined from the dispersion relation as a frequency range in which no propagating (i.e., non-decaying) wave modes exist. However, the notion of a band gap is less clear in dissipative systems, as all wave modes exhibit attenuation. Various measures have been proposed to quantify the “evanescence” of frequency ranges and/or wave propagation directions, but these measures are not based on measurable physical quantities. Furthermore, in finite systems created by truncating a PC, wave propagation is strongly attenuated but not completely forbidden, and a quantitative measure that predicts wave transmission in a finite PC from the infinite dispersion relation is elusive. In this paper, we propose an “evanescence indicator” for PCs with 1D periodicity that relates the decay component of the Bloch wavevector to the transmitted wave amplitude through a finite PC. When plotted over a frequency range of interest, this indicator reveals frequency regions of strongly attenuated wave propagation, which are dubbed “fuzzy band gaps” due to the smooth (rather than abrupt) transition between evanescent and propagating wave characteristics. The indicator is capable of identifying polarized fuzzy band gaps, including fuzzy band gaps which exists with respect to “hybrid” polarizations which consist of multiple simultaneous polarizations. We validate the indicator using simulations and experiments of wave transmission through highly viscoelastic and finite phononic crystals.

Elastic wave band gaps in 2D fractal phononic crystals

2021 ◽  
Author(s):  
Victor Gustavo Ramos Costa Dos Santos ◽  
Edson Jansen Pedrosa de Miranda Junior ◽  
Jose Maria Campos dos Santos
Keyword(s):  
Elastic Wave ◽  
Phononic Crystals ◽  
Band Gaps ◽  
Wave Band

Tunable Band Gaps of Acoustic Waves in Two-Dimensional Phononic Crystals With Reticular Band Structures

2009 ◽  
Author(s):  
Zi-Gui Huang ◽  
Yunn-Lin Hwang ◽  
Pei-Yu Wang ◽  
Yen-Chieh Mao
Keyword(s):  
Acoustic Waves ◽  
Composite Structures ◽  
Phononic Crystals ◽  
Band Gaps ◽  
Sound Insulation ◽  
Two Dimensional ◽  
The Finite Element Method ◽  
Elastic Band ◽  
Band Structures ◽  
Elastic Band Gaps

The excellent applications and researches of so-called photonic crystals raise the exciting researches of phononic crystals. By the analogy between photon and phonon, repetitive composite structures that are made up of different elastic materials can also prevent elastic waves of some certain frequencies from passing by, i.e., the frequency band gap features also exist in acoustic waves. In this paper, we present the results of the tunable band gaps of acoustic waves in two-dimensional phononic crystals with reticular band structures using the finite element method. Band gaps variations of the bulk modes due to different thickness and angles of reticular band structures are calculated and discussed. The results show that the total elastic band gaps for mixed polarization modes can be enlarged or reduced by adjusting the orientation of the reticular band structures. The phenomena of band gaps of elastic or acoustic waves can potentially be utilized for vibration-free, high-precision mechanical systems, and sound insulation.

scholarly journals Formation of Bragg Band Gaps in Anisotropic Phononic Crystals Analyzed With the Empty Lattice Model

Crystals ◽  
2016 ◽  
Vol 6 (5) ◽  
pp. 52 ◽  
Author(s):  
Yan-Feng Wang ◽  
Alexei Maznev ◽  
Vincent Laude
Keyword(s):  
Lattice Model ◽  
Phononic Crystals ◽  
Band Gaps

scholarly journals Wave band gaps in two-dimensional piezoelectric/piezomagnetic phononic crystals

2008 ◽  
Vol 45 (14-15) ◽  
pp. 4203-4210 ◽  
Author(s):  
Yi-Ze Wang ◽  
Feng-Ming Li ◽  
Wen-Hu Huang ◽  
Xiaoai Jiang ◽  
Yue-Sheng Wang ◽  
...  
Keyword(s):  
Phononic Crystals ◽  
Band Gaps ◽  
Wave Band ◽  
Two Dimensional

Maximizing spatial decay of evanescent waves in phononic crystals by topology optimization

2017 ◽  
Vol 182 ◽  
pp. 430-447 ◽  
Author(s):  
Yafeng Chen ◽  
Xiaodong Huang ◽  
Guangyong Sun ◽  
Xiaolei Yan ◽  
Guangyao Li
Keyword(s):  
Topology Optimization ◽  
Evanescent Waves ◽  
Phononic Crystals ◽  
Spatial Decay

scholarly journals Phononic Band Gaps of Elastic Periodic Structures: A Homogenization Theory Study

2007 ◽  
Author(s):  
Ying-Hong Liu ◽  
Chien C. Chang ◽  
Ruey-Lin Chern ◽  
C. Chung Chang
Keyword(s):  
Elastic Constants ◽  
Periodic Structures ◽  
Mass Density ◽  
Density Ratio ◽  
Low Frequency ◽  
Phononic Crystals ◽  
Band Gaps ◽  
Homogenization Theory ◽  
Dominant Factor ◽  
Phononic Band Gaps

In this study, we investigate band structures of phononic crystals with particular emphasis on the effects of the mass density ratio and of the contrast of elastic constants. The phononic crystals consist of arrays of different media embedded in a rubber or epoxy. It is shown that the density ratio rather than the contrast of elastic constants is the dominant factor that opens up phononic band gaps. The physical background of this observation is explained by applying the theory of homogenization to investigate the group velocities of the low-frequency bands at the center of symmetry Γ.

Large band gaps in elastic phononic crystals with air inclusions

2003 ◽  
Vol 83 (19) ◽  
pp. 3900-3902 ◽  
Author(s):  
Yun Lai ◽  
Zhao-Qing Zhang
Keyword(s):  
Phononic Crystals ◽  
Band Gaps
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