Accession Number : ADA131653

Title :   Acoustic Pulse Scattering from Impedance Covered Cylinders.

Descriptive Note : Doctoral thesis,


Personal Author(s) : Khavaran,Abbas

PDF Url : ADA131653

Report Date : Aug 1983

Pagination or Media Count : 136

Abstract : An expression for the acoustic scattered pressure from an impedance covered cylinder due to an incident plane pulse is obtained analytically. The application of Fourier transform on time and subsequent Sommerfield-Watson transformation results in separate expressions for geometrically reflected pressure and for creeping (or circumferential) waves. Using Cauchy contour integration theorem and saddle-point methods, the inverse Fourier transform is evaluated. The impulse response and convolution theorem have been utilized to obtain an expression for the scattered pressure for incident harmonic pulse train and FM pulses. The first arrival of acoustic wave at an observer point in the far field is shown to be due to the geometrically reflected pressure. After the first arrival, creeping waves are shown to circumnavigate the cylinder surface for an indefinite number of times and radiate off tangentially at any angle. These waves create the multiple echoes that return in the scattering of a single pulse. The circumferential waves are shown to decay exponentially as they encircle the cylinder surface. (Author)

Descriptors :   *Acoustic scattering, *Pulses, *Cylindrical bodies, Impedance, Pressure, Fourier transformation, Acoustic waves, Geometry, Theory, Theses, Test and evaluation

Subject Categories : Acoustics

Distribution Statement : APPROVED FOR PUBLIC RELEASE