Low-frequency Wave Propagation in a Periodical Weak-contrast Medium

2013 ◽  
Author(s):  
Y. Roganov ◽  
A. Stovas
Keyword(s):  
Wave Propagation ◽  
Contrast Medium ◽  
Low Frequency ◽  
Frequency Wave

Characteristics of Band Gap and Low-frequency Wave Propagation of Mechanically Tunable Phononic Crystals with Scatterers in Periodic Porous Elastomeric Matrices

2021 ◽  
pp. 1-34
Author(s):  
Shaowu Ning ◽  
Dongyang Chu ◽  
Fengyuan Yang ◽  
Heng Jiang ◽  
Zhanli Liu ◽  
...  
Keyword(s):  
Wave Propagation ◽  
Coupling Effect ◽  
Low Frequency ◽  
Phononic Crystals ◽  
Band Gaps ◽  
Dynamic Responses ◽  
Acoustic Metamaterials ◽  
Frequency Wave ◽  
Strong Coupling Effect ◽  
The Matrix

Abstract The characteristics of passive responses and fixed band gaps of phononic crystals (PnCs) limit their possible applications. For overcoming this shortcoming, a class of tunable PnCs comprised of multiple scatterers and soft periodic porous elastomeric matrices are designed to manipulate the band structures and directionality of wave propagation through the applied deformation. During deformation, some tunable factors such as the coupling effect of scatterer and hole in the matrix, geometric and material nonlinearities, and the rearrangement of scatterer are activated by deformation to tune the dynamic responses of PnCs. The roles of these tunable factors in the manipulation of dynamic responses of PnCs are investigated in detail. The numerical results indicate that the tunability of the dynamic characteristic of PnCs is the result of the comprehensive function of these tunable factors mentioned above. The strong coupling effect between the hole in the matrix and the scatterer contributes to the formation of band gaps. The geometric nonlinearity of matrix and rearrangement of scatterer induced by deformation can simultaneously tune the band gaps and the directionality of wave propagation. However, the matrix's material nonlinearity only adjusts the band gaps of PnCs and does not affect the directionality of wave propagation in them. The research extends our understanding of the formation mechanism of band gaps of PnCs and provides an excellent opportunity for the design of the optimized tunable PnCs and acoustic metamaterials.

Low-frequency wave propagation in an elastic plate floating on a two-layered fluid

Wave Motion ◽  
2016 ◽  
Vol 62 ◽  
pp. 98-113 ◽  
Author(s):  
D.A. Indejtsev ◽  
M.G. Zhuchkova ◽  
D.P. Kouzov ◽  
S.V. Sorokin
Keyword(s):  
Wave Propagation ◽  
Elastic Plate ◽  
Low Frequency ◽  
Frequency Wave ◽  
Layered Fluid

Very low frequency wave propagation numerical model

2013 ◽  
Author(s):  
Guillaume Jamet ◽  
Claude Guennou ◽  
Laurent Guillon ◽  
Jean-Yves Royer
Keyword(s):  
Wave Propagation ◽  
Numerical Model ◽  
Low Frequency ◽  
Frequency Wave ◽  
Very Low Frequency

scholarly journals Simulation of non-hydrostatic gravity wave propagation in the upper atmosphere

2014 ◽  
Vol 32 (4) ◽  
pp. 443-447 ◽  
Author(s):  
Y. Deng ◽  
A. J. Ridley
Keyword(s):  
Wave Propagation ◽  
Gravity Wave ◽  
High Frequency ◽  
General Circulation ◽  
Low Frequency ◽  
Circulation Model ◽  
Horizontal Resolution ◽  
Upper Atmosphere ◽  
Cutoff Wavelength ◽  
Frequency Wave

Abstract. The high-frequency and small horizontal scale gravity waves may be reflected and ducted in non-hydrostatic simulations, but usually propagate vertically in hydrostatic models. To examine gravity wave propagation, a preliminary study has been conducted with a global ionosphere–thermosphere model (GITM), which is a non-hydrostatic general circulation model for the upper atmosphere. GITM has been run regionally with a horizontal resolution of 0.2° long × 0.2° lat to resolve the gravity wave with wavelength of 250 km. A cosine wave oscillation with amplitude of 30 m s−1 has been applied to the zonal wind at the low boundary, and both high-frequency and low-frequency waves have been tested. In the high-frequency case, the gravity wave stays below 200 km, which indicates that the wave is reflected or ducted in propagation. The results are consistent with the theoretical analysis from the dispersion relationship when the wavelength is larger than the cutoff wavelength for the non-hydrostatic situation. However, the low-frequency wave propagates to the high altitudes during the whole simulation period, and the amplitude increases with height. This study shows that the non-hydrostatic model successfully reproduces the high-frequency gravity wave dissipation.

Analysis of Phononic Bandgap Structures With Dissipation

2013 ◽  
Vol 135 (4) ◽  
Author(s):  
Erik Andreassen ◽  
Jakob S. Jensen
Keyword(s):  
Wave Propagation ◽  
Propagation Constant ◽  
Low Frequency ◽  
Homogenization Theory ◽  
Complex Frequency ◽  
Frequency Wave ◽  
Complex Wave ◽  
Viscoelastic Composites ◽  
Periodic Materials ◽  
Loss Factors

We study wave propagation in periodic materials with dissipation using two different formulations. An ω(k)-formulation yields complex frequency solutions for nonvanishing dissipation whereas a k(ω)-formulation leads to complex wave numbers. For small (realistic) levels of material dissipation and longer wavelengths, we show that the two formulations produce nearly identical results in terms of propagation constant and wave decay. We use the k(ω)-formulation to compute loss factors with dissipative bandgap materials for steady-state wave propagation and create simplified diagrams that unify the spatial loss factor from dissipative and bandgap effects. Additionally, we demonstrate the applicability of the k(ω)-formulation for the computation of the band diagram for viscoelastic composites and compare the computed loss factors for low frequency wave propagation to existing results based on quasi-static homogenization theory.

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