ABSTRACT
Many researchers have investigated the assembly of equal-size spheres because of its simplicity and its convenience in theoretical work. The particle shape especially surface roughness of a particle is affected on particle packing structure. Regular packing is the easiest to use to describe internal structure as a set of unit cells. Knowledge of the spatial structure of particles in a random assembly is important in dealing with the deformation of a powder bed, the electrostatic and liquid bridge forces between particles, radiative and convective heat transfer in particle systems, and so on. Actual powders have wide distributions in size; hence, a packed bed can be regarded as a mixture of different-size particles. Particle size distribution also effect void fraction. Generally speaking, powder has a random structure, and regular packing hardly exists in practice.
