scholarly journals Reflection coefficient null of acoustic waves at a liquid–anisotropic‐solid interface

1989 ◽  
Vol 85 (1) ◽  
pp. 1-10 ◽  
Author(s):  
Orhan Arikan ◽  
Emre Telatar ◽  
Abdullah Atalar
Keyword(s):  
Reflection Coefficient ◽  
Acoustic Waves ◽  
Solid Interface ◽  
Anisotropic Solid

scholarly journals Damping and reflection coefficient measurements for an open pipe at low Mach and low Helmholtz numbers

1993 ◽  
Vol 256 ◽  
pp. 499-534 ◽  
Author(s):  
M. C. A. M. Peters ◽  
A. Hirschberg ◽  
A. J. Reijnen ◽  
A. P. J. Wijnands
Keyword(s):  
Experimental Data ◽  
Reflection Coefficient ◽  
Strouhal Number ◽  
Acoustic Waves ◽  
High Frequency ◽  
Nonlinear Behaviour ◽  
Mean Flow ◽  
Frequency Limit ◽  
Low Frequencies ◽  
Open Pipe

The propagation of plane acoustic waves in smooth pipes and their reflection at open pipe terminations have been studied experimentally. The accuracy of the measurements is determined by comparison of experimental data with results of linear theory for the propagation of acoustic waves in a pipe with a quiescent fluid. The damping and the reflection at an unflanged pipe termination are compared.In the presence of a fully developed turbulent mean flow the measurements of the damping confirm the results of Ronneberger & Ahrens (1977). In the high-frequency limit the quasi-laminar theory of Ronneberger (1975) predicts accurately the convective effects on the damping of acoustic waves. For low frequencies a simple theory combining the rigid-plate model of Ronneberger & Ahrens (1977) with the theoretical approach of Howe (1984) yields a fair prediction of the influence of turbulence on the shear stress. The finite response time of the turbulence near the wall to the acoustic perturbations has to be taken into account in order to explain the experimental data. The model yields a quasi-stationary limit of the damping which does not take into account the fundamental difference between the viscous and thermal dissipation observed for low frequencies.Measurements of the nonlinear behaviour of the reflection properties for unflanged pipe terminations with thin and thick walls in the absence of a mean flow confirm the theory of Disselhorst & van Wijngaarden (1980), for the low-frequency limit. It appears however that a two-dimensional theory such as proposed by Disselhorst & van Wijngaarden (1980) for the high-frequency limit underestimates the acoustical energy absorption by vortex shedding by a factor 2.5.The measured influence of wall thickness on the reflection properties of an open pipe end confirms the linear theory of Ando (1969). In the presence of a mean flow the end correction δ of an unflanged pipe end varies from the value at the high-Strouhal-number limit of δ/a = 0.61, with a the pipe radius, which is close to the value in the absence of a mean flow given by Levine & Schwinger (1948) of δ/a = 0.6133, to a value of δ/a = 0.19 in the low-Strouhal-number limit which is close to the value predicted by Rienstra (1983) of δ/a = 0.26.The pressure reflection coefficient is found to agree with the theoretical predictions by Munt (1977, 1990) and Cargill (1982b) in which a full Kutta condition is included. The accuracy of the theory is fascinating in view of the dramatic simplifications introduced in the theory. For a thick-walled pipe end and a pipe terminated by a horn the end correction behaviour is similar. It is surprising that the nonlinear behaviour at low frequencies and high acoustic amplitudes in the absence of mean flow does not influence the end correction significantly.The aero-acoustic behaviour of the pipe end is dramatially influenced by the presence of a horn. In the presence of a mean flow the horn is a source of sound for a critical range of the Strouhal number.The high accuracy of the experimental data suggests that acoustic measurements can be used for a systematic study of turbulence in unsteady flow and of unsteady flow separation.

Surface acoustic waves at the vacuum-thermoviscoelastic solid interface

Ultrasonics ◽  
2000 ◽  
Vol 37 (10) ◽  
pp. 677-680 ◽  
Author(s):  
M. Deschamps ◽  
O. Poncelet ◽  
S. Dilhaire ◽  
W. Claeys
Keyword(s):  
Acoustic Waves ◽  
Surface Acoustic Waves ◽  
Solid Interface

scholarly journals Reflection of acoustic waves from the boundary or layer of two-phase medium

2018 ◽  
Vol 148 ◽  
pp. 15005
Author(s):  
D.A. Gubaidullin ◽  
D.D. Gubaidullina ◽  
Yu.V. Fedorov
Keyword(s):  
Reflection Coefficient ◽  
Acoustic Wave ◽  
Acoustic Waves ◽  
Finite Thickness ◽  
Low Frequency ◽  
Bubbly Liquid ◽  
Pure Liquid ◽  
Angle Of Incidence ◽  
Two Phase ◽  
Low Frequencies

The inclined incidence of the acoustic wave on a layer of gas-droplet mixture or bubbly liquid of finite thickness is theoretically investigated. In the case of the incidence of the low-frequency acoustic wave to interface between the pure gas and aerosol or to interface between pure liquid and bubbly liquid the basic laws of reflection and transmission of a wave are established. This circumstance allows us to evaluate the transmission and reflection coefficients, depending on the volume content of inclusions and the angle of incidence of the acoustic wave. In particular, for the interface between pure gas and aerosol analytical expressions of the critical angle of wave incidence at which reflection coefficient becomes zero are obtained, i.e. thus there is a complete passage of the acoustic wave through the interface. It is established that the increase of the angle of incidence of the acoustic wave on the boundary or layer of aerosol causes: first, either to increase or to decrease of the reflection coefficient at low frequencies, and second, to appearance of additional minima depending on the reflection coefficient from frequency of disturbances related to the difference of speed of sound and density of the medium.

RESONANCES OF ACOUSTIC WAVES INTERACTING WITH AN ELASTIC SEABED

2001 ◽  
Vol 09 (03) ◽  
pp. 1079-1093 ◽  
Author(s):  
MARGARETE S. FOKINA ◽  
VLADIMIR N. FOKIN
Keyword(s):  
Reflection Coefficient ◽  
Half Space ◽  
Acoustic Waves ◽  
Elastic Half Space ◽  
Exact Expression ◽  
Ocean Bottom ◽  
Sediment Layer ◽  
Resonance Theory ◽  
Space Characteristic ◽  
Exact Calculations

An exact expression for the reflection coefficient is obtained with the Thomson–Haskell technique for the geoacoustical model of an ocean bottom consisting of an elastic homogeneous sediment layer overlying an elastic half-space. Characteristic equations for explicit determination of the position of each individual resonance contribution to the reflection coefficient are derived. Analytical expressions for the angular and frequency resonance positions are found. The resonance expression for the reflection coefficient is written in the form of a sum of resonance terms. Comparison between resonance theory and exact calculations for the elastic layer covering the elastic half-space is presented. The results of resonance formalism show excellent agreement with exact theory in all the cases.

Orientational plasticity at a smectic-liquid-crystal–anisotropic-solid interface

1992 ◽  
Vol 45 (10) ◽  
pp. R6981-R6984 ◽  
Author(s):  
Zhiming Zhuang ◽  
Noel A. Clark ◽  
Michael R. Meadows
Keyword(s):  
Liquid Crystal ◽  
Solid Interface ◽  
Smectic Liquid Crystal ◽  
Anisotropic Solid

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

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.

Sign in / Sign up

Export Citation Format

Share Document