摘要:

This paper considers the time‐averaged acoustic force exerted on a spherical liquid droplet in an acoustic stationary wave. Experimental and theoretical values are presented for the minimum acoustic pressure amplitudes required to trap small individual droplets of various liquids near the pressure antinodes of a stationary sound field in a cylinder filled with water. The liquids used were paraldehyde, hexane, benzene, toluene, chlorobenzene, and carbon tetrachloride. Droplet radii ranged from 400 to 800 μ, and acoustic‐pressure amplitudes required to trap the droplets ranged from 1 to 15 bars. Calculated and observed values for the acoustic force are in substantial agreement, provided the compressibility of the liquid droplets is considered.

ISSN:0001-4966    

DOI:10.1121/1.1912614

出版商:Acoustical Society of America    

年代:1971

数据来源: AIP

摘要:

The attenuation of ultrasonic waves was measured in single crystals of naphthalene from 23° to −185°C for frequencies from 15 to 45 MHz. A maximum was observed in the absorption coefficient at low temperatures, and from the frequency dependence of the absorption, the result was examined in terms of relaxation phenomena. The experimental results are compared to the relaxation maximum predicted by the Liebermann theory assuming the temperature‐cubed term of the transition probability to be the dominant temperature dependence. The transition probability is calculated from the experimental data and compared directly to the theoretical values. Also, a transition probability with exponential temperature dependence is shown to agree equally as well with the experimental results.

ISSN:0001-4966    

DOI:10.1121/1.1912615

出版商:Acoustical Society of America    

年代:1971

数据来源: AIP

摘要:

Wave propagation in an inhomogeneous elastic half‐space is investigated. Integral expressions for vertical and horizontal displacement due to a point source have been obtained in terms of reflection coefficients for a medium in which compressional‐ and shear‐wave velocities increase monotonically with depth. These expressions are further shown to reduce to known expressions in the case of homogeneous solid and stratified liquid.

ISSN:0001-4966    

DOI:10.1121/1.1912616

出版商:Acoustical Society of America    

年代:1971

数据来源: AIP

摘要:

The effect of a layer on surface wave propagation on a half‐space can be separated into terms arising from elastic and from inertial restraining forces. In a number of situations of practical importance, it turns out that the inertial terms are dominant. The period equations governing the dispersion for this pure mass loading are obtained in suitable form and numerical solutions for Rayleigh waves for both solid and fluid loading are obtained. It is shown that by presenting the results in terms of appropriate variables, extremely simple, approximately linear, dispersion characteristics are found. A single computation suffices for substrate materials having the same Poisson ratio. The validity of this approximation is explored for modified Rayleigh waves for both solid and liquid layers, and for Love waves.

ISSN:0001-4966    

DOI:10.1121/1.1912617

出版商:Acoustical Society of America    

年代:1971

数据来源: AIP

摘要:

The debate about scattering of interaction‐frequency components when two sound waves interact at a non‐zero angle has not been resolved because no positive evidence of such scattering outside the interaction volume has been put forward. In this contribution, an attempt is made to review the situation in view of the available experimental evidence relating to interaction between a plane wave and a “collimated” pump wave.

ISSN:0001-4966    

DOI:10.1121/1.1912618

出版商:Acoustical Society of America    

年代:1971

数据来源: AIP

摘要:

The choice ofPandSdesignations is somewhat arbitrary in heterogeneous elastic media, but becomes precise in the high‐frequency limit of ray theory. This fact is used in a radially heterogeneous isotropic medium to establish three potentials (P,S,T) with the following properties: (1) every displacement solution is represented by some (P,S,T); (2)T(r,t) is decoupled fromPandS, is a potential forSHmotion, and satisfies second‐order wave equation; and (3) the coupling ofPandSVis represented by coupled equations in potentialsPandS. At high frequencies these equations decouple (for an important class of sources) into separate second‐order wave equations forPandS. An important role, in this decoupled case, is played by the variable density. Several possibilities suggested by the generalPandSVequations are also outlined.

ISSN:0001-4966    

DOI:10.1121/1.1912619

出版商:Acoustical Society of America    

年代:1971

数据来源: AIP

摘要:

A circular cylindrical viscoelastic solid tube filled with a compressible viscous fluid is considered. The outer surface of the tube is assumed to be constrained so that it cannot move freely. Axially symmetric wave solutions are obtained for the linearized equations governing the motion of the fluid and the solid. The solutions lead to a complicated transcendental dispersion equation relating the wave frequency and the propagation constant. This equation is simplified by taking the fluid to be inviscid and the tube to be thin. Then it is studied by both analytical and numerical means. Formulas and graphs are given for the propagation constant, the phase velocity, the group velocity, etc., as functions of the frequency for various sets of parameter values. There are infinitely many modes of propagation, two of which are “tube modes” and the rest of which are acoustic modes. The case of a viscous fluid and a tube of any thickness are to be treated in a subsequent paper.

ISSN:0001-4966    

DOI:10.1121/1.1912620

出版商:Acoustical Society of America    

年代:1971

数据来源: AIP

摘要:

The effects of high‐intensity electromagnetic energy deposition in solids can be catastrophic. Among the mechanisms which could be considered as thermal shock wave mitigators is the dissipative mechanism of thermoelastic damping. In order to assess this concept, a coupled linear one‐dimensional thermoelastic problem with a volumetric heat input is solved by an approximate technique. The problem corresponds to the impulsive heating of a partially transparent (to radiative flux) medium. The approximate solution has the correct behavior for small and large times, satisfies the boundary conditions, and duplicates the behavior of the discontinuities in the field variables (in particular, the stress field). For parameters in the range of physical interest, the solution obtained here differs little from the uncoupled solution, with one exception. In this case, the effect of thermoelastic coupling is essentially to remove the discontinuities from the fields so that changes in the neighborhood of the wavefront are rapid but continuous. Failure criteria are essentially unaffected, since the peak tensile stress is very nearly the same for coupled and uncoupled solutions.

ISSN:0001-4966    

DOI:10.1121/1.1912621

出版商:Acoustical Society of America    

年代:1971

数据来源: AIP

摘要:

The approximate thin‐shell theory of Herrmann and Mirsky is used to study stress wave propagation in a thin‐walled cylindrical tube due to sudden release of a concentrated ring pressure. The tube is assumed to be of infinite length, so that the problem is a pure initial‐value problem for which the solution can be represented as a superposition of harmonic plane waves. Numerical results are plotted for profiles of strains, stress resultants, and displacements versus distance along the tube axis at several times after the load is released.

ISSN:0001-4966    

DOI:10.1121/1.1912622

出版商:Acoustical Society of America    

年代:1971

数据来源: AIP

摘要:

The vibration of a thin cylindrical duct, due to an internal random pressure field caused by airflow, was studied both experimentally and theoretically. The Reynolds number for the experiments was near 105and the Mach number was less than 0.1, typical of large air handling applications. Although a muffler was used to simulate acoustically a much longer duct, the acoustic pressure was found to be a significant cause of duct vibration. A simple model (white noise) of the pressure field was convolved with the dynamic Green's function of the duct to compute numerically the radial displacement cross covariances. In spite of this simplification, the measured displacement covariances were in good agreement with those calculated. The displacement spectral density was predicted to vary as ω−3with white‐noise excitation. The observed dependence was ω−4.8and was accounted for by the fact that the forcing function was not white noise, but had a frequency dependence near ω−2.

ISSN:0001-4966    

DOI:10.1121/1.1912623

出版商:Acoustical Society of America    

年代:1971

数据来源: AIP