First‐order reflection coefficient of surface acoustic waves from thin‐strip overlays

AbstractIn this paper, the problem of interface wave scattering by bottom undulations in the presence of a thin submerged vertical wall with a gap is investigated. The thin vertical wall with a gap is submerged in a lower fluid of finite depth with bottom undulations and the upper fluid is of infinite height separated by a common interface. In the method of solution, we use a simplified perturbation analysis and suitable applications of Green’s integral theorem in the two fluid regions produce first-order reflection and transmission coefficients in terms of integrals involving the shape function describing the bottom undulations and solution of the scattering problem involving a submerged vertical wall present in the lower fluid of uniform finite depth. For sinusoidal bottom undulations, the first-order transmission coefficient vanishes identically. The corresponding first-order reflection coefficient is computed numerically by solving the zero-order reflection coefficient and a suitable application of multi-term Galerkin approximations. The numerical results of the zero-order and first-order reflection coefficients are depicted graphically against the wave number in a number of figures. An oscillatory nature is observed of first-order reflection coefficient due to multiple interactions of the incident wave with bottom undulations, the edges of the submerged wall and the interface. The first-order reflection coefficient has a peak value for some particular value of the ratio of the incident wavelength and the bottom wavelength. The presence of the upper fluid has some significant effect on the reflection coefficients.

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Analysis of the Reflection Coefficient of Rayleigh Waves From Surface-Breaking Cracks

10.1115/imece2000-1642 ◽

2000 ◽

Author(s):

Waled Hassan ◽

William Veronesi

Keyword(s):

Reflection Coefficient ◽

Rayleigh Wave ◽

Acoustic Waves ◽

Near Field ◽

Crack Depth ◽

Wave Length ◽

Surface Acoustic Waves ◽

Finite Size ◽

High Crack ◽

Limiting Value

Abstract The interaction of surface acoustic waves with finite-size, surface-breaking, semi-circular cracks is studied theoretically, numerically, and experimentally. We focus on the behavior of the reflection coefficient of the Rayleigh wave from such cracks in both the far and near fields of the crack. It is shown that, in the near field, the reflection coefficient from such cracks is higher than the reflection coefficient measured in the far field. This is mainly due to the diverging nature of the Rayleigh wave reflected from the crack. In the high crack depth to wave length ratio, the finite element and experimental results approach the limiting value of the reflection coefficient from a 90-degree corner.

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Subwavelength Acoustic Valley-Hall Topological Insulators Using Soda Cans Honeycomb Lattices

Research ◽

10.34133/2019/5385763 ◽

2019 ◽

Vol 2019 ◽

pp. 1-8 ◽

Cited By ~ 1

Author(s):

Zhiwang Zhang ◽

Ye Gu ◽

Houyou Long ◽

Ying Cheng ◽

Xiaojun Liu ◽

...

Keyword(s):

Phase Transition ◽

Acoustic Waves ◽

Surface Acoustic Waves ◽

Honeycomb Lattice ◽

Inversion Symmetry ◽

Edge States ◽

Dual Frequency ◽

Dirac Cone ◽

First Order ◽

Scale Size

Topological valley-contrasting physics has attracted great attention in exploring the use of the valley degree of freedom as a promising carrier of information. Recently, this concept has been extended to acoustic systems to obtain nonbackscattering sound propagations. However, previous demonstrations are limited by the cut-off frequency of 2D waveguides and lattice-scale size restrictions since the topological edge states originate from Bragg interference. Here we engineer topologically valley-projected edge states in the form of spoof surface acoustic waves that confine along the surface of a subwavelength honeycomb lattice composed of 330-mL soda cans. The inversion symmetry is broken through injecting a certain amount of water into one of the two cans in each unit cell, which gaps the Dirac cone and ultimately leads to the topological valley-Hall phase transition. Dual-frequency ranges of the valley-projected edge states below the sound line are observed, which originate from the first-order and second-order resonances, respectively. These results have the potential to enable promising routes to design integrated acoustic devices based on valley-contrasting physics.

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Numerical study of acoustophoretic manipulation of particles in microfluidic channels

Proceedings of the Institution of Mechanical Engineers Part H Journal of Engineering in Medicine ◽

10.1177/09544119211024775 ◽

2021 ◽

pp. 095441192110247

Author(s):

Jun Ma ◽

Dongfang Liang ◽

Xin Yang ◽

Hanlin Wang ◽

Fangda Wu ◽

...

Keyword(s):

Acoustic Waves ◽

Acoustic Radiation ◽

Numerical Study ◽

Surface Acoustic Waves ◽

Radiation Force ◽

Suspended Particles ◽

Bottom Surface ◽

Microfluidic Channels ◽

The Finite Element Method ◽

First Order

The microfluidic technology based on surface acoustic waves (SAW) has been developing rapidly, as it can precisely manipulate fluid flow and particle motion at microscales. We hereby present a numerical study of the transient motion of suspended particles in a microchannel. In conventional studies, only the microchannel’s bottom surface generates SAW and only the final positions of the particles are analyzed. In our study, the microchannel is sandwiched by two identical SAW transducers at both the bottom and top surfaces while the channel’s sidewalls are made of poly-dimethylsiloxane (PDMS). Based on the perturbation theory, the suspended particles are subject to two types of forces, namely the Acoustic Radiation Force (ARF) and the Stokes Drag Force (SDF), which correspond to the first-order acoustic field and the second-order streaming field, respectively. We use the Finite Element Method (FEM) to compute the fluid responses and particle trajectories. Our numerical model is shown to be accurate by verifying against previous experimental and numerical results. We have determined the threshold particle size that divides the SDF-dominated regime and the ARF-dominated regime. By examining the time scale of the particle movement, we provide guidelines on the device design and operation.

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SURFACE WAVE SCATTERING BY AN ELASTIC PLATE SUBMERGED IN WATER WITH UNEVEN BOTTOM

Mathematical Modelling and Analysis ◽

10.3846/mma.2020.10315 ◽

2020 ◽

Vol 25 (3) ◽

pp. 323-337

Author(s):

Souvik Kundu ◽

Rupanwita Gayen

Keyword(s):

Reflection Coefficient ◽

Elastic Plate ◽

Flexural Rigidity ◽

Bottom Topography ◽

Integral Theorem ◽

First Order ◽

Bottom Undulation ◽

Rigidity Parameter ◽

Vertical Elastic Plate ◽

Order Reflection

Wave interaction with a vertical elastic plate in presence of undulating bottom topography is considered, assuming linear theory and utilizing simple perturbation analysis. First order correction to the velocity potential corresponding to the problem of scattering by a vertical elastic plate submerged in a fluid with a uniform bottom is obtained by invoking the Green’s integral theorem in a suitable manner. With sinusoidal undulation at the bottom, the first-order transmission coefficient (T1) vanishes identically. Behaviour of the first order reflection coefficient (R1) depending on the plate length, ripple number, ripple amplitude and flexural rigidity of the plate is depicted graphically. Also, the resonant nature of the first order reflection is observed at a particular value of the ratio of surface wavelength to that of the bottom undulations. The net reflection coefficient due to the joint effect of the plate and the bottom undulation is also presented for different flexural rigidity of the plate. When the rigidity parameter is made sufficiently large, the results for R1 reduce to the known results for a surface piercing rigid plate in water with bottom undulation.

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Characterization of RF Sputtered ZnO Piezoelectric Films Using Transmission Electron Microscope

Proceedings, annual meeting, Electron Microscopy Society of America ◽

10.1017/s0424820100114050 ◽

1975 ◽

Vol 33 ◽

pp. 86-87

Author(s):

Kemining W. Yeh ◽

Richard S. Muller ◽

Wei-Kuo Wu ◽

Jack Washburn

Keyword(s):

Integrated Circuit ◽

Acoustic Waves ◽

New Technology ◽

Surface Acoustic Waves ◽

Electromechanical Properties ◽

Leading Role ◽

Saw Devices ◽

Transmission Electron ◽

High Degree

Considerable and continuing interest has been shown in the thin film transducer fabrication for surface acoustic waves (SAW) in the past few years. Due to the high degree of miniaturization, compatibility with silicon integrated circuit technology, simplicity and ease of design, this new technology has played an important role in the design of new devices for communications and signal processing. Among the commonly used piezoelectric thin films, ZnO generally yields superior electromechanical properties and is expected to play a leading role in the development of SAW devices.

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