The newly developed "void expansion method" allows for an efficientgeneration of porous packings of spherical particles over a wide range ofvolume fractions using the discrete element method. Particles are randomlyplaced under addition of much smaller "void-particles". Then, the void-particleradius is increased repeatedly, thereby rearranging the structural particlesuntil formation of a dense particle packing. The structural particles' mean coordination number was used to characterizethe evolving microstructures. At some void radius, a transition from aninitially low to a higher mean coordination number is found, which was used tocharacterize the influence of the various simulation parameters. For structuraland void-particle stiffnesses of the same order of magnitude, the transition isfound at constant total volume fraction slightly below the random close packinglimit. For decreasing void-particle stiffness the transition is shifted towardsa smaller void-particle radius and becomes smoother.
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