Gago Paula A, Maza Diego, Pugnaloni Luis A
Departamento de Ingeniería Mecánica, Facultad Regional La Plata, Universidad Tecnológica Nacional, Av. 60 Esq. 124, 1900 La Plata, Argentina.
Consejo Nacional de Investigaciones Científicas y Técnicas, Argentina.
Phys Rev E Stat Nonlin Soft Matter Phys. 2015 Mar;91(3):032207. doi: 10.1103/PhysRevE.91.032207. Epub 2015 Mar 30.
We investigate the steady-state packing fraction ϕ and force moment tensor Σ of quasi-two-dimensional granular columns subjected to tapping. Systems of different height h and width L are considered. We find that ϕ and Σ, which describe the macroscopic state of the system, are insensitive to L for L>50d (with d the grain diameter). However, results for granular columns of different heights cannot be conciliated. This suggests that comparison between results of different laboratories on this type of experiments can be done only for systems of same height. We show that a parameter ɛ=1+(Aω)2/(2gh), with A and ω the amplitude and frequency of the tap and g the acceleration of gravity, can be defined to characterize the tap intensity. This parameter is based on the effective flight of the granular bed, which takes into account the h dependency. When ϕ is plotted as a function of ɛ, the data collapses for systems of different h. However, this parameter alone is unable to determine the steady state to be reached since different Σ can be observed for a given ɛ if different column heights are considered.
我们研究了受敲击的准二维颗粒柱的稳态堆积分数ϕ和力矩张量Σ。考虑了不同高度h和宽度L的系统。我们发现，对于L>50d（d为颗粒直径），描述系统宏观状态的ϕ和Σ对L不敏感。然而，不同高度颗粒柱的结果无法协调一致。这表明，只有对于相同高度的系统，不同实验室在这类实验上的结果才能进行比较。我们表明，可以定义一个参数ɛ=1+(Aω)2/(2gh)，其中A和ω分别为敲击的振幅和频率，g为重力加速度，以表征敲击强度。该参数基于颗粒床的有效飞行，考虑了h的依赖性。当将ϕ绘制为ɛ的函数时，不同h的系统的数据会合并在一起。然而，仅这个参数无法确定要达到的稳态，因为如果考虑不同的柱高，对于给定的ɛ可以观察到不同的Σ。
