Skip to main content
U.S. flag

An official website of the United States government

Official websites use .gov
A .gov website belongs to an official government organization in the United States.

Secure .gov websites use HTTPS
A lock ( ) or https:// means you’ve safely connected to the .gov website. Share sensitive information only on official, secure websites.

Contact function, uniform-thickness shell volume, and convexity measure for 3D star-shaped random particles

Published

Author(s)

Edward J. Garboczi, Jeffrey W. Bullard

Abstract

Using a spherical harmonic series, the three-dimensional shape of star-shaped particles can be represented mathematically as readily as can a sphere, cube, or ellipsoid. In principle, any particle parameter, such as volume, surface area, moment of inertia tensor, or integrated mean curvature, can be easily computed. In this paper, we extend this list by developing three important algorithms, which have been found useful for regular particles, and adapting them to the case of random star-shaped particles using spherical harmonic series. These three algorithms are: a two-particle contact function, how to add a uniform-thickness shell to a single particle, and estimation of the convexity of a single particle using an algorithm for computing the convex hulls of non-convex particles. A derivation and numerical examples are shown for each algorithm. The two-particle contact function may be used in random particle placement programs, so that random-shaped particles may be used in suspension models as readily as spheres or ellipsoids. New results are shown for how the volume of a uniform-thickness shell, normalized by the surface area of the original particle, depends on the shell thickness t. For a sphere, the exact expression is cubic in t, with the linear coefficient unity and the quadratic coefficient equal to the reciprocal of the sphere radius. For star-shaped particles, the coefficient of the linear term is also unity and the coefficient of the quadratic term in t seems to be equal, within a few percent, to the reciprocal of the radius of the volume-equivalent sphere. The convexity measure, using convex hulls, adds to the list of useful shape parameters for random star-shaped particles and is shown to distinguish between different particle sets.
Citation
Powder Technology
Volume
237

Keywords

contact function, particles, convexity, shell, spherical harmonics, algorithm, overlap

Citation

Garboczi, E. and Bullard, J. (2013), Contact function, uniform-thickness shell volume, and convexity measure for 3D star-shaped random particles, Powder Technology (Accessed June 18, 2024)

Issues

If you have any questions about this publication or are having problems accessing it, please contact reflib@nist.gov.

Created March 15, 2013, Updated February 19, 2017