Rigid Body Dynamics Algorithm for Modeling Random Packing Structures of Nonspherical and Nonconvex Pellets

Despite
the common use of nonspherical catalyst pellets in chemical
engineering applications, the packing structures of such pellets have
not been as systematically studied and characterized as spherical
packings. We propose a packing algorithm based on rigid body dynamics
to simulate packing of nonspherical and possibly nonconvex pellets.
The algorithm exerts a hard-body approach to model collision phenomena.
The novelty is that the transition between moving and resting particles
is controlled by a cutoff on the relative contact velocities, instead
of artificially damping linear and angular velocities to stabilize
the algorithm. The algorithm is used to synthesize packings of spheres,
cylinders, and Raschig rings with tube-to-pellet diameter ratios 3–9.16.
The packings are validated in terms of bulk porosity and radial void
fraction distribution, finding satisfactory agreement with literature
data. Denser packing structures are generated with high restitution
coefficients and low friction coefficients. The confining tube walls
play an important role, with highly fluctuating bulk porosities in
narrow tubes.