Accession Number:

ADA222179

Title:

Low-Frequency Scattering by Correlated Distributions of Randomly Oriented Particles

Descriptive Note:

Corporate Author:

ILLINOIS UNIV AT CHICAGO CIRCLE DEPT OF MATHEMATICS

Personal Author(s):

Report Date:

1987-05-01

Pagination or Media Count:

10.0

Abstract:

Random distributions of correlated scatterers averaged over orientation are considered, corresponding to isotropic fluids of statistical mechanics particles with volume v, number concentration p, and volume fraction w pv. For minimum separation of centers small compared to wavelength and acoustic particle parameters close to the embedding mediums, the incoherent differential scattering from unit volume and the corresponding attenuation coefficient are proportional to the fluctuations variance in number concentration. For arbitrary convex hard particles e.g., ovals or simple polyhedra, repulsive at contact with shape parameter c or 3, the variance is expressed in terms of a quotient Scw of polynomials in w that has a maximum S1 c at w1 c. Spheres c 3 were considered earlier. For c 3, the fluctuations and S1 and w1 are smaller than for spheres for c 3 which we consider formally, they are larger than for spheres. The results are interpreted by comparing leading terms with the second virial coefficients for more general statistical mechanics models. Scattering data for suspensions of discoidal red blood cells versus w under different flow conditions can be fitted adequately by Scw for different values of c 3. The low values of c suggest weaker repulsion between deformable cells, and attractive interparticle forces mediated by flow and aggregative trends. Reprints. jhd

Subject Categories:

  • Acoustics

Distribution Statement:

APPROVED FOR PUBLIC RELEASE