Transient Acoustic Wave Propagation In Stratified Fluids PDF Download
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Author | : Calvin H. Wilcox |
Publisher | : |
Total Pages | : 49 |
Release | : 1981 |
Genre | : |
ISBN | : |
Download Transient Acoustic Wave Propagation in Stratified Fluids Book in PDF, ePub and Kindle
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)
Author | : Calvin H. Wilcox |
Publisher | : |
Total Pages | : 50 |
Release | : 1979 |
Genre | : |
ISBN | : |
Download Transient Acoustic Wave Propagation in an Epstein Duct Book in PDF, ePub and Kindle
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)
Author | : Calvin H. Wilcox |
Publisher | : Springer Science & Business Media |
Total Pages | : 206 |
Release | : 2012-12-06 |
Genre | : Technology & Engineering |
ISBN | : 1461211247 |
Download Sound Propagation in Stratified Fluids Book in PDF, ePub and Kindle
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.
Author | : Calvin H. Wilcox |
Publisher | : Springer |
Total Pages | : 212 |
Release | : 1984-04-23 |
Genre | : Mathematics |
ISBN | : 9780387909868 |
Download Sound Propagation in Stratified Fluids Book in PDF, ePub and Kindle
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.
Author | : |
Publisher | : |
Total Pages | : 562 |
Release | : 1992 |
Genre | : Aeronautics |
ISBN | : |
Download Scientific and Technical Aerospace Reports Book in PDF, ePub and Kindle
Author | : Zine El Abiddine |
Publisher | : |
Total Pages | : |
Release | : 2013 |
Genre | : Technology |
ISBN | : |
Download Transient Acoustic Wave Propagation in Porous Media Book in PDF, ePub and Kindle
Transient Acoustic Wave Propagation in Porous Media.
Author | : |
Publisher | : |
Total Pages | : 208 |
Release | : 1980 |
Genre | : Science |
ISBN | : |
Download Technical Abstract Bulletin Book in PDF, ePub and Kindle
Author | : Korey Kilburn |
Publisher | : |
Total Pages | : 72 |
Release | : 2010 |
Genre | : Engineering |
ISBN | : |
Download A Laplace Transform/potential-theoretic Method for Transient Acoustic Propagation in Three-dimensional Subsonic Flows Book in PDF, ePub and Kindle
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.
Author | : Ricardo Weder |
Publisher | : Springer Science & Business Media |
Total Pages | : 196 |
Release | : 2012-12-06 |
Genre | : Science |
ISBN | : 1461244307 |
Download Spectral and Scattering Theory for Wave Propagation in Perturbed Stratified Media Book in PDF, ePub and Kindle
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.
Author | : Calvin H. Wilcox |
Publisher | : |
Total Pages | : 96 |
Release | : 1976 |
Genre | : |
ISBN | : |
Download Spectral and Asymptotic Analysis of Acoustic Wave Propagation Book in PDF, ePub and Kindle
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.