剪切非弹性硬球中的碰撞统计
Collision statistics in sheared inelastic hard spheres
摘要：
采用非平衡分子动力学模拟和直接模拟Monte Carlo方法研究了剪切非弹性-硬球系统的动力学行为。在分子动力学模拟中，Lees-Edwards边界条件用于施加剪切。选择模拟箱的尺寸，以确保系统是均匀的，并且均匀地施加剪切。各种系统属性进行监测，包括单粒子速度分布，颗粒温度，应力张量，碰撞率，碰撞之间的时间。单粒子速度分布被认为是同意合理的各向异性高斯分布，只有轻微的人口过剩的高速尾巴。速度分布是强烈的各向异性，特别是在较低的密度和较低的恢复恢复系数值，在剪切方向上的最大方差。剪切非弹性硬球系统的压缩因子的密度依赖性与弹性硬球流体非常相似。随着系统变得更加非弹性，掠射碰撞开始主导更直接的正面碰撞。对碰撞之间时间分布的研究表明，在高度非弹性系统中，粒子所经历的碰撞是强相关的。模拟数据的比较与DSMC模拟的Enskog方程。Montanero等人的动力学模型的结果{[}Montanero等人，J.FluidMech.389，391（1999）{]}中的方法。在一般情况下，良好的协议被发现为高密度，弱非弹性系统。
英文摘要：
The dynamics of sheared inelastic-hard-sphere systems are studied using non-equilibrium molecular dynamics simulations and direct simulation Monte Carlo. In the molecular dynamics simulations Lees-Edwards boundary conditions are used to impose the shear. The dimensions of the simulation box are chosen to ensure that the systems are homogeneous and that the shear is applied uniformly. Various system properties are monitored, including the one-particle velocity distribution, granular temperature, stress tensor, collision rates, and time between collisions. The one-particle velocity distribution is found to agree reasonably well with an anisotropic Gaussian distribution, with only a slight overpopulation of the high velocity tails. The velocity distribution is strongly anisotropic, especially at lower densities and lower values of the coefficient of restitution, with the largest variance in the direction of shear. The density dependence of the compressibility factor of the sheared inelastic hard sphere system is quite similar to that of elastic hard sphere fluids. As the systems become more inelastic, the glancing collisions begin to dominate more direct, head-on collisions. Examination of the distribution of the time between collisions indicates that the collisions experienced by the particles are strongly correlated in the highly inelastic systems. A comparison of the simulation data is made with DSMC simulation of the Enskog equation. Results of the kinetic model of Montanero et al. {[}Montanero et al., J. Fluid Mech. 389, 391 (1999){]} based on the Enskog equation are also included. In general, good agreement is found for high density, weakly inelastic systems.
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