关于离散元法计算参数的探讨

计算时步、接触刚度等计算参数的选取对离散元法解的正确与否至关重要,目前普遍采用的方法是先确定接触刚度并选取保险系数后,按照经验公式求得计算时步,但在保险系数的设定上有关文献却不尽相同.作者提出了一种新的方法———恢复系数检验法来选定计算参数.采用离散元法最常用的弹性-阻尼-滑动接触模型编制了计算程序,以颗粒同静置平面之间的正碰撞考察了不同计算参数下的模拟结果,除模拟得到恢复系数外,还考察了碰撞过程的总接触时间和总接触时步数.统计分析结果表明:计算时步是影响模拟精度最重要的因素;模拟误差还同恢复系数的设定值有关,设定值越大,模拟误差就越小;计算时步的大小虽然对碰撞过程的总接触时间影响不大,但是却决定了碰撞过程的总接触时步数,二者之间存在对数线性相关关系.

Discussion on the Calculation Parameters of Discrete Element Method

Time step and contact rigidity are important calculation parameters of Discrete Element Method.At present,the contact rigidity and the safety factor are firstly determined and then time step is generally calculated by the empirical formula,but the related literatures are different in the safety factor setting.A new method—restitution coefficient verifying method is put forward.By adopting the spring-dashpot-slide contact model,a program is developed and the simulation results under different calculation parameters for vertical collision between particles and immobile plate are studied.Besides the restitution coefficient gained by the simulation,the total contact time and the total contact step in the course of collision are also studied.Statistic analysis result shows that the time step is the most important influence factor of simulation precision,and there is relation between simulation error and the setup value of restitution coefficient which the greater the setup value is,the less the simulation error is.Although there is no effect to the total contact time in the course of collision,the value of the time step decides the total contact step,and there is a logarithmic linear correlativity between them.