Download or read book Transient Acoustic Wave Propagation in Stratified Fluids written by Calvin H. Wilcox and published by . This book was released on 1981 with total page 49 pages. Available in PDF, EPUB and Kindle. Book excerpt: Transient acoustic wave propagation is analyzed for the case of plane-stratified fluids having density rho(y) and sound speed c(y) at depth y. For infinite fluids it is assumed that the (in general discontinuous) functions rho(y), c(y) are uniformly positive and bounded and satisfy abs.val (rho(y) - rho(at infinity)) or = C(+ or - y) to the - alpha power, abs. val. (c(y) - c(at infinity)) or = C(+ or - y) to the - alpha power for + or - y 0, where alpha 3/2. Semi-infinite and finite layers are also treated. The acoustic potential is a solution of the wave equation del-squared u/del t-squared - c-squared(y) rho(y) del dot (1/rho(y)grad(u)) = f(t, x, y) where x = (x1,x2) are horizontal coordinates and f(t, x, y) characterizes the wave sources. The principal results of the analysis show that u is the sum of a free component, which behaves like a diverging spherical wave for large t, and a guided component which is approximately localized in regions abs. val. (y - y sub j)
Download or read book Transient Acoustic Wave Propagation in an Epstein Duct written by Calvin H. Wilcox and published by . This book was released on 1979 with total page 50 pages. Available in PDF, EPUB and Kindle. Book excerpt: Transient acoustic wave propagation is analyzed for the case of an unlimited plane-stratified fluid having constant density and sound speed c(y) at depth y given by the Epstein profile 1/c(y)-squared = K sech-squared (y/H) + L tanh (y/H) + M. The acoustic potential is a solution of the wave equation Dt-squared u - C-squared (y) (D1-squared u + D2-squared u + Dy-squared u) = f(t, x, y) where x = (x1,x2) are horizontal coordinates and f(t, x, y) characterizes the wave sources. The principal results of the analysis show that u is the sum of a free component, which behaves like a diverging spherical wave for large t, and a guided component which is approximately localized in a region abs. val. (y-y sub 0)
Download or read book Sound Propagation in Stratified Fluids written by Calvin H. Wilcox and published by Springer Science & Business Media. This book was released on 2012-12-06 with total page 206 pages. Available in PDF, EPUB and Kindle. Book excerpt: Stratified fluids whose densities, sound speeds and other parameters are functions of a single depth coordinate occur widely in nature. Indeed, the earth's gravitational field imposes a stratification on its atmosphere, oceans and lakes. It is well known that their stratification has a profound effect on the propagation of sound in these fluids. The most striking effect is probably the occurrence of acoustic ducts, due to minima of the sound speed, that can trap sound waves and cause them to propagate hori zontally. The reflection, transmission and distortion of sonar signals by acoustic ducts is important in interpreting sonar echoes. Signal scattering by layers of microscopic marine organisms is important to both sonar engi neers and marine biologists. Again, reflection of signals from bottom sediment layers overlying a penetrable bottom are of interest both as sources of unwanted echoes and in the acoustic probing of such layers. Many other examples could be given. The purpose of this monograph is to develop from first principles a theory of sound propagation in stratified fluids whose densities and sound speeds are essentially arbitrary functions of the depth. In physical terms, the propagation of both time-harmonic and transient fields is analyzed. The corresponding mathematical model leads to the study of boundary value problems for a scalar wave equation whose coefficients contain the pre scribed density and sound speed functions.
Download or read book Sound Propagation in Stratified Fluids written by Calvin H. Wilcox and published by Springer. This book was released on 1984-04-23 with total page 212 pages. Available in PDF, EPUB and Kindle. Book excerpt: Stratified fluids whose densities, sound speeds and other parameters are functions of a single depth coordinate occur widely in nature. Indeed, the earth's gravitational field imposes a stratification on its atmosphere, oceans and lakes. It is well known that their stratification has a profound effect on the propagation of sound in these fluids. The most striking effect is probably the occurrence of acoustic ducts, due to minima of the sound speed, that can trap sound waves and cause them to propagate hori zontally. The reflection, transmission and distortion of sonar signals by acoustic ducts is important in interpreting sonar echoes. Signal scattering by layers of microscopic marine organisms is important to both sonar engi neers and marine biologists. Again, reflection of signals from bottom sediment layers overlying a penetrable bottom are of interest both as sources of unwanted echoes and in the acoustic probing of such layers. Many other examples could be given. The purpose of this monograph is to develop from first principles a theory of sound propagation in stratified fluids whose densities and sound speeds are essentially arbitrary functions of the depth. In physical terms, the propagation of both time-harmonic and transient fields is analyzed. The corresponding mathematical model leads to the study of boundary value problems for a scalar wave equation whose coefficients contain the pre scribed density and sound speed functions.
Download or read book Scientific and Technical Aerospace Reports written by and published by . This book was released on 1992 with total page 562 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Download or read book Transient Acoustic Wave Propagation in Porous Media written by Zine El Abiddine and published by . This book was released on 2013 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt: Transient Acoustic Wave Propagation in Porous Media.
Download or read book Technical Abstract Bulletin written by and published by . This book was released on 1980 with total page 208 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Download or read book A Laplace Transform potential theoretic Method for Transient Acoustic Propagation in Three dimensional Subsonic Flows written by Korey Kilburn and published by . This book was released on 2010 with total page 72 pages. Available in PDF, EPUB and Kindle. Book excerpt: This dissertation presents the development of a semi-analytic technique developed for the determination of far field acoustic radiation in the time domain. This method solves linear, time dependent wave propagation in an unbounded medium using a numerical Laplace transform and potential theory. The end result is a robust procedure that is accurate and computationally efficient. The Transform Potential Theoretic (TPT) method is meshless and can handle arbitrary geometries. The procedure assumes the linearity of the sound field away from a bounded region surrounding the object. The TPT method depends on the sound pressure on the boundary of this region (referred to as the Kirchhoff surface). The Euler equations are linearized about a uniform mean flow. First, the problem is transformed via the Laplace transform (with appropriate initial conditions) into a reduced wave equation. By application of a dependent variable transformation, the anisotropic terms are removed and a Helmholtz-like equation with complex wave number is obtained where both single and double layer potential theory applies. This allows the calculation of the far-field acoustic pressure in the Laplace domain. Then, an inversion of the dependent variable transform is applied. Upon application of numerical inverse Laplace transform techniques, far-field acoustic pressure is then successfully obtained as a function of space and time. Using transient monopole radiation in a uniform freestream, accuracy is analyzed with excellent results. This method shows many advantages over direct simulation, including vast savings in computational time. The freestream Mach number is only a parameter in the TPT method and has no bearing on the run time, unlike direct methods.
Download or read book Spectral and Scattering Theory for Wave Propagation in Perturbed Stratified Media written by Ricardo Weder and published by Springer Science & Business Media. This book was released on 2012-12-06 with total page 196 pages. Available in PDF, EPUB and Kindle. Book excerpt: The propagation of acoustic and electromagnetic waves in stratified media is a subject that has profound implications in many areas of applied physics and in engineering, just to mention a few, in ocean acoustics, integrated optics, and wave guides. See for example Tolstoy and Clay 1966, Marcuse 1974, and Brekhovskikh 1980. As is well known, stratified media, that is to say media whose physical properties depend on a single coordinate, can produce guided waves that propagate in directions orthogonal to that of stratification, in addition to the free waves that propagate as in homogeneous media. When the stratified media are perturbed, that is to say when locally the physical properties of the media depend upon all of the coordinates, the free and guided waves are no longer solutions to the appropriate wave equations, and this leads to a rich pattern of wave propagation that involves the scattering of the free and guided waves among each other, and with the perturbation. These phenomena have many implications in applied physics and engineering, such as in the transmission and reflexion of guided waves by the perturbation, interference between guided waves, and energy losses in open wave guides due to radiation. The subject matter of this monograph is the study of these phenomena.
Download or read book The Shock and Vibration Digest written by and published by . This book was released on 1980 with total page 660 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Download or read book Spectral and Asymptotic Analysis of Acoustic Wave Propagation written by Calvin H. Wilcox and published by . This book was released on 1976 with total page 96 pages. Available in PDF, EPUB and Kindle. Book excerpt: The report presents an exposition of the results of the author's research on acoustic wave propagation during the last five years. The principal result of this research is the 'method of spectral and asymptotic analysis' for determining the structure of acoustic waves in unbounded media. In this report the method is explained and illustrated by its application to the following four classes of acoustic wave propagation problems: Scattering by bounded obstacles in a homogeneous unlimited fluid; propagation and scattering in simple and compound tubular waveguides; propagation in plane stratified fluids; propagation in crystals.
Download or read book Scattering of transient acoustic waves in fluids and solids written by Gerard Cornelis Herman and published by . This book was released on 1981 with total page 183 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Download or read book Spectral Analysis of Sound Propagation in Stratified Fluids written by Calvin H. Wilcox and published by . This book was released on 1980 with total page 156 pages. Available in PDF, EPUB and Kindle. Book excerpt: This paper presents a spectral analysis of the acoustic fields in stationary plane stratified fluids whose densities and sound speeds are functions of the depth. The analysis is based on families of normal mode fields that have simple physical interpretations. The acoustic field in such a fluid may be described by an acoustic potential or by the excess pressure.
Download or read book Materials and Acoustics Handbook written by Michel Bruneau and published by John Wiley & Sons. This book was released on 2013-05-10 with total page 704 pages. Available in PDF, EPUB and Kindle. Book excerpt: Written by a group of acoustics and vibration specialists, this book studies the acoustic and vibrating phenomena that occur in diverse materials used for all kinds of purposes. The first part studies the fundamental aspects of propagation: analytical, numerical and experimental. The second part outlines industrial and medical applications. Covering a wide range of topics that associate materials science with acoustics, this will be of invaluable use to researchers, engineers, or practitioners in this field, as well as students in acoustics, physics, and mechanics.
Download or read book Theoretical And Computational Acoustics 95 written by Ding Lee and published by World Scientific. This book was released on 1996-08-30 with total page 581 pages. Available in PDF, EPUB and Kindle. Book excerpt: This conference provided a forum for active researchers to discuss the state-of-the-art in theoretical and computational acoustics. Topics covered fluid/elastic interface-theoretical and computational aspects with applications, seismic waves and earthquake studies, modeling, theoretical and computational aspects for multidimensional wave propagation, methods for computational acoustics, structural acoustics, scattering and inverse problems, solutions to acoustic problems by supercomputers and parallel processing, and application of neural networks to acoustics.
Download or read book Applied Mechanics Reviews written by and published by . This book was released on 1965 with total page 654 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Download or read book Reviews in Partial Differential Equations 1980 86 as Printed in Mathematical Reviews written by and published by . This book was released on 1988 with total page 722 pages. Available in PDF, EPUB and Kindle. Book excerpt:
