The clustering behavior of a mono-disperse granular gas is experimentally studied in an asymmetric two-compartment setup. Unlike the random clustering in either compartment in the case of symmetric configuration when lowering the shaking strength to below a critical value, the directed clustering is observed, which corresponds to an imperfect pitchfork bifurcation. Numerical solutions of the flux equation using a modified simple flux function show qualitative agreements with the experimental results. The potential application of this asymmetric structure is discussed.
The definition and the previous measurements of a dynamics-relevant temperature-like quantity in granular media are reviewed for slow and fast particle systems. Especially, the validity of the fluctuation-dissipation theorem in such an athermal system is explored. Experimental evidences for the fluctuation-dissipation theorem relevant effect temperature support the athermal statistical mechanics, which has been widely explored in recent years by physicists. Difficulties encountered in defining temperature or establishing thermodynamics or statistical mechanics in non-equilibrium situations are discussed.
In this paper,granular segregation in a two-compartment cell in zero gravity is studied numerically by DEM simulation.In the simulation using a virtual window method we find a non-monotonic flux,a function which governs the segregation.A parameter is used to quantify the segregation.The effect of three parameters:the total number of particles N,the excitation strength F,and the position of the window coupling the two compartments,on the segregation and the waiting time%are investigated.It is found that the segregation observed in zero gravity exists and does not depend on the excitation strength F.The waiting time T,however,depends strongly on F:the higher the F,the lower the waiting time V,The simulation results are important in guiding the SJ-10 satellite microgravity experiments.
