The anisotropy of free path in a vibro-fluidized granular gas

Abstract

The free path of a vibro-fluidized two-dimensional (2D) inelastic granular gas confined in a rectangular box is investigated by 2D event-driven molecular simulation. By tracking particles in the simulation, we analyze the local free path. The probability distribution of the free path shows a high tail deviating from the exponential prediction. The anisotropy of the free path is found when we separate the free path to x and y components. The probability distribution of y component is exponential, while x component has a high tail. The probability distribution of angle between the relative velocity and the unit vector joined two particle centers deviates from the distribution of two random vectors, indicating the existence of the dynamic heterogeneities in our system. We explain these results by resorting to the kinetic theory with two-peak velocity distribution. The kinetic theory agrees well with the simulation result.

Chain structure of head-on collisions in boundary driven granular gases

“…There are two peaks clearly located at −1 and 1 for P (cos Ψ ′ ), respectively, in our system. It is obvious the probability of head-on collisions is higher than that of the oblique one, which is consistent with above results and our previous event-driven molecular dynamic simulation results [5]. It need to mention that P (cos Ψ ′ ) between translational and rotational velocities [20] in uniform shear flow has a peak at 0, which is reasonable because that the uniform case is dominated by grazing-collision.…”

“…In the case of a granular gas confined between two vibrating walls without gravity, the system form a spatially gradient fields with the distance of the energizing boundary. What's more, there are gradual velocity distributions [2][3][4]( from two-peak near the boundary layer to one peak in the center layer), and abnormal large local mean free paths [5] near the boundary. These represent a long range boundary effect [6,7].…”

Experimental and numerical study on energy dissipation in freely cooling granular gases under microgravity

“…From a homogeneous excited-state, the system enters into an initial period of homogeneous energy loss, and later grains can spontaneously cluster. [1][2][3][4][5][6][7][8][9][10][11][12][13][14][15][16][17] Theoretical modeling, [18][19][20][21][22][23][24][25][26][27][28][29] and simulation investigations [20][21][22]24,28,[30][31][32][33][34][35][36][37][38][39] are based on simplifications and assumptions of grain properties. Quantitative experiments are very much needed for better understanding of fundamental features of such ensembles.…”