Accession Number : ADA257257


Title :   Scattering and Radiation by Shells and Nonlinear Acoustics of Particle Suspensions


Descriptive Note : Final rept. 15 Jul 1989-30 Sep 1992


Corporate Author : WASHINGTON STATE UNIV PULLMAN DEPT OF PHYSICS


Personal Author(s) : Marston, Philip L


Full Text : https://apps.dtic.mil/dtic/tr/fulltext/u2/a257257.pdf


Report Date : 23 Oct 1992


Pagination or Media Count : 69


Abstract : The research reported concerns three main areas: (a) Surface Guided Wave Contributions to the Scattering of Sound by Elastic Shells in Water Quantitative ray representations described for the scattering by shells give insight into the coupling of sound with structures. backscattering enhancement near the coincidence frequency was observed, modeled, shown to be due to a subsonic wave. Aspects of a high-frequency enhancement were investigated along with time-frequency spectrograms of the impulse response. (b) Radiation Mechanisms for Evanescent Tone Bursts on Fluid Loaded Membranes and Plates Subsonic flexural waves on unbounded plates ordinarily produce evanescent wavefields in the surrounding fluid that are trapped to the plate. Two mechanisms for radiating sound were investigated experimentally: (a) diffraction by a rigid barrier in an evanescent field in air and (b) transition radiation produced when a wave packet travels down a vertical plate through a water surface. (c) Acoustical Four-Wave Mixing in Suspensions Sound is shown to interact with sound in a suspension of microspheres. The spheres are attracted to pressure nodes of counter-propagating pump waves. The banded suspension acts as a diffraction grating and scatters a probe-wave when a Bragg condition is satisfied. Acoustical Scattering, Ray Methods, Elastic Shells, Evanescent Waves, Plates, Suspensions, Nonlinear Acoustics, Radiation Pressure.


Descriptors :   *ACOUSTIC WAVES , *ACOUSTIC SCATTERING , *ELASTIC SHELLS , FREQUENCY , RADIATION , SCATTERING , HIGH FREQUENCY , PACKETS , WATER , STRUCTURES , AUGMENTATION , BACKSCATTERING , SHELLS(STRUCTURAL FORMS) , SPHERES , RUPTURE , SURFACES , GRATINGS(SPECTRA) , WAVE PROPAGATION , DIFFRACTION , CYLINDRICAL BODIES , PLATES , RESPONSE , PRESSURE , MEMBRANES , ACOUSTICS , MIXING , TRANSITIONS , PUMPS , UNDERWATER ACOUSTICS , COUPLINGS , WAVE PACKETS , RADIATION PRESSURE , EVANESCENT WAVES , MICROSPHERES


Subject Categories : Structural Engineering and Building Technology
      Acoustics


Distribution Statement : APPROVED FOR PUBLIC RELEASE