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May 1990

Volume 87, Issue S1, pp. S1-S164

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back to top Session DDD. Physical Acoustics VIII: Acoustics in Multicomponent Media
Contributed Papers
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Asymptotic series for disparate mixtures (A)

Gregory Gillette

J. Acoust. Soc. Am. Volume 87, Issue S1, pp. S139-S139 (1990); (1 page) | Cited 1 time

Online Publication Date: 13 Aug 2005

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The term “disparate mixture” here refers to a physical mixture composed of two distinct phases, where the physical properties of the phases are very dissimilar. It might be formed, e.g., from two immiscible gases or fluids, or from a soil‐water compound. The calculation of fields in such a mixture is discussed, leading to the development of a pair of coupled asymptotic series (corresponding to the field point in one or the other of the phases). The specific problem of acoustic wave fields due to a point source in a two‐fluid mixture illustrates the procedure. Questions of interest are: How does the mixture behave away from the limiting case, i.e., when the property ratio of the phases is very small but nonzero? How are successive terms in the series related to geometric length scales in the mixture (connectivity scales, inclusion size scales, matrix “gap” scales)? Preliminary results of applying the method to the reflection of plane waves from a flat interface are presented, and extensions to additional layered mixture models are indicated.
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Sound wave propagation through multiphase materials (A)

W. H. Schwarz and T. S. Marguiles

J. Acoust. Soc. Am. Volume 87, Issue S1, pp. S139-S139 (1990); (1 page)

Online Publication Date: 13 Aug 2005

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Theories for infinitesimal, planar sound wave propagation in a dilute suspension of rigid particles in a viscous fluid has been investigated by generally three approaches: (1) wave scattering, (2) hydrodynamic, and (3) ad hoc approaches specific to particular systems. Here, a hydrodynamic development that uses spatially averaged continuum balance and constitutive equations for multiphase materials is presented. Two alternative approaches derive equivalent results (i.e., a bicubic polynomial equation) for the complex propagation constant χ  =  − (a + ik), where a is the spatial attenuation coefficient and k is the wavenumber. One approach uses linear momentum equations for each individual phase, while the other uses an overall linear momentum equation and a relative momentum equation, obtained by taking the sum and difference of the individual momentum equations for the continuous and particulate phases. The advantage of this latter aproach is that it expresses the results in the form of a generalized Fick′s law, and expresses the diffusion of particles, as well as the supply terms such as barophoresis, thermophoresis, and pycnophoresis, explicitly. Furthermore, an Einstein relation can be obtained by simply defining a diffusion coefficient, and interpreting this coefficient in the linear momentum supply term that is proportional to the relative velocity as a Stokes viscous drag force.
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Measurement and calculation of acoustic propagation constants in arrays of air‐filled rectangular tubes (A)

Heui‐Seol Roh, James M. Sabatier, Richard Raspet, and W. Patrick Arnott

J. Acoust. Soc. Am. Volume 87, Issue S1, pp. S139-S139 (1990); (1 page)

Online Publication Date: 13 Aug 2005

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The theory of sound propagation in rigid cylindrical tubes is established by the separate treatments of viscous and thermal effects [K. Attenborough, J. Acoust. Soc. Am. 73, 785–799 (1983)]. Such development is applied to investigate the theory of sound propagation in rigid rectangular tubes. Arrays of air‐filled rigid parallel rectangular tubes are prepared to compare the theory with the measurements of propagation constants. [Roh et al., J. Acoust. Soc. Am. Suppl. 1 85, S82 (1989)]. The theoretical calculation of complex propagation constants is compared with experimental data as a function of frequency. The dynamic shape factor, which is related to deviation of propagation constants in cylindrical tube cross sections, is examined by comparison of propagation theories between rectangular and circular tubes. [Work supported by ONR and USA‐CERL.]
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Measurement of tortuosity of porous materials and implications for acoustical modeling (A)

Yvan Champoux and Michael R. Stinson

J. Acoust. Soc. Am. Volume 87, Issue S1, pp. S139-S139 (1990); (1 page) | Cited 1 time

Online Publication Date: 13 Aug 2005

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Tortuosity is one of several physical parameters required by various theoretical models to characterize the acoustical behavior of a porous material. In this paper, an experimental system that permits rapid and convenient measurement of the tortuosity of materials is described. A five‐terminal conductivity technique is applied to samples of porous material saturated with an electrolyte. Measurements of voltages between three judiciously installed inner electrodes (silver wire), coupled with independent measurement of sample porosity, are sufficient to determine the tortuosity. The current electrodes are different than the voltage terminals, so voltage drops associated with the electrochemical processes at these electrodes are not important. Consequently, the measurements of tortuosity are not affected by the amount of current used or the conductivity of the electrolyte. Experimental results, using several calibration samples with known tortuosity, confirm that tortuosity can be measured using this approach with a 2%–3% accuracy. Acoustical measurements (characteristic impedance and propagation constant) on a model porous material having pores of varying cross‐sectional area are used to illustrate the importance of using the measured tortuosity in application of theoretical models.
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Measurements of elastic constants of ceramic composites using ultrasonic plate mode antiresonances (A)

W. Wang and S. I. Rokhlin

J. Acoust. Soc. Am. Volume 87, Issue S1, pp. S139-S140 (1990); (2 pages)

Online Publication Date: 13 Aug 2005

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With oblique incidence of an ultrasonic wave upon a thin anisotropic plate immersed in fluid, in general the quasilongitudinal, flexural, and quasi‐SH vibrations are excited. At some angles of incidence, coherent interactions of these waves lead to antiresonance‐type minima of the normal displacement on the back surface of the plate and therefore to minima of the transmission coefficient. At off‐axis orientations of the thin anisotropic plate relative to the incidence plane, several minima may be found. One of them may be used for shear modulus measurement. The measurements have been performed on (1) a porous aluminum oxide membrane, which is transversely isotropic in the plane of the membrane, and (2) a unidirectional SiC/Al composite membrane, where the fibers lie in the plane of the plate. The elastic constants were extracted from the experimental data by a nonlinear least‐squares optimization technique. It is demonstrated that the method gives very good results for determination of in‐plane longitudinal and shear moduli.
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On the estimation of the acoustic surface impedance of layered porous materials (A)

W. Lauriks, J. F. Allard, and A. Cops

J. Acoust. Soc. Am. Volume 87, Issue S1, pp. S140-S140 (1990); (1 page)

Online Publication Date: 13 Aug 2005

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The acoustic impedance of layered porous materials can be calculated using the Biot theory and a matrix formalism to characterize each layer. A comparison with experimental data will be made for layered systems of various types, including layered systems covered with a membrane. The experimental data have been obtained with a two‐microphone technique, which calculates the acoustic impedance from pressure measurements at two different microphone locations above the sample.
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Anomalous ultrasonic behavior of hydrogen‐bonded liquid binary systems containing Ortho Chlorophenol (A)

Janjanam S. Ramamurthy

J. Acoust. Soc. Am. Volume 87, Issue S1, pp. S140-S140 (1990); (1 page)

Online Publication Date: 13 Aug 2005

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Ultrasonic absorption and velocity have been measured in a number of binary hydrogen‐bonded liquid systems of which Ortho Chlorophenol forms a common constituent. The composition and temperature dependence of absorption and velocity bear a remarkable similarity to those observed in aqueous hydrogen‐bonded liquid binary systems. Pronounced absorption peaks, maxima in velocity, and negative excess compressibilities followed by peaks of shear viscosity and liberation of considerable heats of mixing are attributed to the formation of a metastable intermediate state with a sound sensitive structural equilibirum. A modified two‐state model is proposed for quantitative interpretation of results.
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