Study On Physical Properties Of Non-uniform Granular System

Granular-material system here is two-phase systems composed of macroscopical particles with different sizes (e.g. coffee, powders, and detritus, etc.). Problems in granular systems are roughly divided into quasi-static (sand piles, distribution of static forces, compaction, and fracture propagation, etc.) and dynamical ones (all kinds of flows, convection, and segregation, pattern formation, and fluidized beds, etc.) [1]. Aiming at the latter, the research has been made for the non-uniform granular system, which was dealt with in the different dynamics regimes: quasi-equilibrium regime and far from equilibrium one. It should to be emphasized that, for resolving the physical problems on non-uniform granular system, the velocity distribution function with the fractal character was originally put forward with the dense-gas kinetic theory and fractal theory. In the quasi-equilibrium regime, granular hydrokinetics theory [3-6] is brought forward based on dense-gas kinetic theory [2]. In this theory, particles are looked as slick balls with uniform size; granular sizes and surface forms will not bring any influences to the characteristics of the system. However, experiments showed that, for many materials, in the procession of macroscopical comminution, the geometrical and mathematical characteristics exhibited the self-similarity [7-8]. On the base of the fractal model for non-uniform granular system [9-10], the velocity distribution function with the fractal character was put forward under the quasi-equilibrium regime. Furthermore, we investigated the thermal conductivity in the mixed system. Found that the thermal conductivity changed with the solid fraction , structural character parameter and fractal dimension .The increasing power of computer awakened an interest in the "granular gases" simulation, in the far from equilibrium regime, which more really reflects the dynamics characteristics of granular systems [11-14]. The numerical results performed many different properties from the granular hydrokinetics theory: the velocity distribution deviates the Gaussian and the spatial clusterization arises. Monte Carlo simulation made in this paper also exhibited that the degree of inhomogeneity in the granularity distribution signed by the fractal dimension of size distribution has great influences on the dynamics actions of the system. The velocity distribution deviates obviously from the Gaussian distribution and the particles cluster more pronounced with the larger value of in the system. The work in this paper generalized the research from the simple granular system to the non-uniform one. The more important is that the predictions in our work make the new programs for correlative experiments.