Azéma Emilien, Radjaï Farhang, Peyroux Robert, Dubois Frédéric, Saussine Gilles
LMGC, CNRS - Université Montpellier II, Place Eugène Bataillon, 34095 Montpellier Cedex 05, France.
Phys Rev E Stat Nonlin Soft Matter Phys. 2006 Sep;74(3 Pt 1):031302. doi: 10.1103/PhysRevE.74.031302. Epub 2006 Sep 13.
By means of two-dimensional contact dynamics simulations, we analyze the vibrational dynamics of a confined granular layer in response to harmonic forcing. We use irregular polygonal grains allowing for strong variability of solid fraction. The system involves a jammed state separating passive (loading) and active (unloading) states. We show that an approximate expression of the packing resistance force as a function of the displacement of the free retaining wall from the jamming position provides a good description of the dynamics. We study in detail the scaling of displacements and velocities with loading parameters. In particular, we find that, for a wide range of frequencies, the data collapse by scaling the displacements with the inverse square of frequency, the inverse of the force amplitude, and the square of gravity. Interestingly, compaction occurs during the extension of the packing, followed by decompaction in the contraction phase. We show that the mean compaction rate increases linearly with frequency up to a characteristic frequency and then it declines in inverse proportion to frequency. The characteristic frequency is interpreted in terms of the time required for the relaxation of the packing through collective grain rearrangements between two equilibrium states.
通过二维接触动力学模拟，我们分析了受限颗粒层在谐波激励下的振动动力学。我们使用不规则多边形颗粒，以允许固体分数有很大的变化。该系统涉及一个将被动（加载）状态和主动（卸载）状态分开的堵塞状态。我们表明，作为自由挡土墙从堵塞位置的位移的函数的堆积阻力的近似表达式能够很好地描述动力学。我们详细研究了位移和速度随加载参数的标度关系。特别地，我们发现，在很宽的频率范围内，通过用频率的平方反比、力幅的倒数和重力的平方来标度位移，数据会塌缩到一起。有趣的是，压实发生在堆积扩展期间，随后在收缩阶段发生解压。我们表明，平均压实率在达到一个特征频率之前随频率线性增加，然后与频率成反比下降。特征频率是根据通过两个平衡态之间的集体颗粒重排使堆积松弛所需的时间来解释的。
