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Jun 2005

Volume 117, Issue 6, pp. 3335-3971

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Identification of laser generated acoustic waves in the two-dimensional transient response of cylinders

Y. Pan, C. Rossignol, and B. Audoin

J. Acoust. Soc. Am. Volume 117, Issue 6, pp. 3600-3608 (2005); (9 pages) | Cited 2 times

Online Publication Date: 31 May 2005

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The published model [Appl. Phys. Lett. 82, 4379–4381 (2003)] for the two-dimensional transient wave propagation in a cylinder is modified to avoid the inherited integration of the numerical inverse scheme. The Fourier series expansion is introduced for one spatial coordinate to resolve the transient response problem: theoretical radial displacements in either the ablation or the thermoelastic regime are obtained with little numerical noise and short computation time. The normal mode expansion method fails to deliver results with the same accuracy. Acoustic waves are fully identified by the ray trajectory analysis. These identified waves are further verified on the experimental results observed with the laser ultrasonic technique. © 2005 Acoustical Society of America.
Show PACS
43.35.Cg Ultrasonic velocity, dispersion, scattering, diffraction, and attenuation in solids; elastic constants
43.20.Px Transient radiation and scattering
43.20.Bi Mathematical theory of wave propagation

Shear-horizontal acoustic wave propagation in piezoelectric bounded plates with metal gratings

Shi Chen, Tiantong Tang, and Zhaohong Wang

J. Acoust. Soc. Am. Volume 117, Issue 6, pp. 3609-3615 (2005); (7 pages)

Online Publication Date: 31 May 2005

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In this paper, shear-horizontal (SH) acoustic wave propagation in metal gratings deposited on piezoelectric bounded plates is investigated. The spectral characteristics of the electromechanical coupling coefficient are studied first, which are very important for acoustic wave device designs. And, an effective mathematic method based on even- and odd base functions is also presented for overcoming the large frequency thickness product problem. Then, the characteristics of the grating modes are studied, and the nature and characteristics of the stop bands are investigated fully. The results show that the width and attenuation of the stop bands are dominated by the electromechanical coupling coefficient at the frequency centers of the stop bands. © 2005 Acoustical Society of America.
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43.35.Ns Acoustical properties of thin films
43.35.Pt Surface waves in solids and liquids
43.35.Cg Ultrasonic velocity, dispersion, scattering, diffraction, and attenuation in solids; elastic constants

Fast calculation of pulsed photoacoustic fields in fluids using k-space methods

B. T. Cox and P. C. Beard

J. Acoust. Soc. Am. Volume 117, Issue 6, pp. 3616-3627 (2005); (12 pages) | Cited 16 times

Online Publication Date: 31 May 2005

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Two related numerical models that calculate the time-dependent pressure field radiated by an arbitrary photoacoustic source in a fluid, such as that generated by the absorption of a short laser pulse, are presented. Frequency-wavenumber (k-space) implementations have been used to produce fast and accurate predictions. Model I calculates the field everywhere at any instant of time, and is useful for visualizing the three-dimensional evolution of the wave field. Model II calculates pressure time series for points on a straight line or plane and is therefore useful for simulating array measurements. By mapping the vertical wavenumber spectrum directly to frequency, this model can calculate time series up to 50 times faster than current numerical models of photoacoustic propagation. As the propagating and evanescent parts of the field are calculated separately, model II can be used to calculate far- and near-field radiation patterns. Also, it can readily be adapted to calculate the velocity potential and thus particle velocity and acoustic intensity vectors. Both models exploit the efficiency of the fast Fourier transform, and can include the frequency-dependent directional response of an acoustic detector straightforwardly. The models were verified by comparison with a known analytic solution and a slower, but well-understood, numerical model. © 2005 Acoustical Society of America.
Show PACS
43.35.Ud Thermoacoustics, high temperature acoustics, photoacoustic effect
43.20.Px Transient radiation and scattering

An aeroacoustically driven thermoacoustic heat pump

W. V. Slaton and J. C. H. Zeegers

J. Acoust. Soc. Am. Volume 117, Issue 6, pp. 3628-3635 (2005); (8 pages) | Cited 1 time

Online Publication Date: 31 May 2005

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The mean flow of gas in a pipe past a cavity can excite the resonant acoustic modes of the cavity—much like blowing across the top of a bottle. The periodic shedding of vortices from the leading edge of the mouth of the cavity feeds energy into the acoustic modes which, in turn, affect the shedding of the next vortex. This so-called aeroacoustic whistle can excite very high amplitude acoustic standing waves within a cavity defined by coaxial side branches closed at their ends. The amplitude of these standing waves can easily be 20% of the ambient pressure at optimal gas flow rates and ambient pressures within the main pipe. A standing wave thermoacoustic heat pump is a device which utilizes the in-phase pressure and displacement oscillations to pump heat across a porous medium thereby establishing, or maintaining, a temperature gradient. Experimental results of a combined system of aeroacoustic sound source and a simple thermoacoustic stack will be presented. © 2005 Acoustical Society of America.
Show PACS
43.35.Ud Thermoacoustics, high temperature acoustics, photoacoustic effect
43.28.Ra Generation of sound by fluid flow, aerodynamic sound and turbulence
43.20.Ks Standing waves, resonance, normal modes
43.25.Vt Intense sound sources
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