  Granular packing structures of cohesive micro-sized particles with different
sizes and size distributions, including mono-sized, uniform and Gaussian
distribution, are investigated by using two different history dependent contact
models with Discrete Element Method (DEM). The simulation is carried out in the
framework of LIGGGHTS which is a DEM simulation package extended based on
branch of granular package of widely used open-source code LAMMPS. Contact
force caused by translation and rotation, frictional and damping forces due to
collision with other particles or container boundaries, cohesive force, van der
Waals force, and gravity are considered. The radial distribution functions
(RDFs), force distributions, porosities, and coordination numbers under
cohesive and non-cohesive conditions are reported. The results indicate that
particle size and size distributions have great influences on the packing
density for particle packing under cohesive effect: particles with Gaussian
distribution have the lowest packing density, followed by the particles with
uniform distribution; the particles with mono-sized distribution have the
highest packing density. It is also found that cohesive effect to the system
does not significantly affect the coordination number that mainly depends on
the particle size and size distribution. Although the magnitude of net force
distribution is different, the results for porosity, coordination number and
mean value of magnitude of net force do not vary significantly between the two
contact models.
