The n-body instability is investigated with the soft-sphere discrete element method. The divergence of nearby trajectories is quantified by the dynamical memory time. Using the inverse proportionality between the dynamical memory time and the largest Lyapunov exponent, the soft-sphere discrete element method results are compared to previous hard-sphere molecular dynamics data for the first time. Good agreement is observed at low concentrations and the degree of instability is shown to increase asymptotically with increasing spring stiffness. At particle concentrations above 30%, the soft-sphere Lyapunov exponents increase faster than the corresponding hard-sphere data, hypothesized to be caused by relatively rare multi-particle collisions. This paper concludes with a demonstration of how this case study may be used in conjunction with regression testing and code verification activities.

该ñ使用软球离散元方法研究 - 体不稳定性。附近轨迹的发散由动态记忆时间量化。利用动态记忆时间与最大李雅普诺夫指数之间的反比关系，首次将软球离散元方法的结果与以前的硬球分子动力学数据进行了比较。在低浓度下观察到良好的一致性，并且不稳定性程度随着弹簧刚度的增加而逐渐增加。当粒子浓度高于 30% 时，软球李雅普诺夫指数的增加速度比相应的硬球数据更快，假设是由相对罕见的多粒子碰撞引起的。