Schmick Malte, Markus Mario
Max-Planck-Institut für Molekulare Physiologie, Postfach 500247, Dortmund, Germany.
Phys Rev E Stat Nonlin Soft Matter Phys. 2008 Jul;78(1 Pt 1):010302. doi: 10.1103/PhysRevE.78.010302. Epub 2008 Jul 23.
We investigate experimentally a homogeneously driven granular medium. It consists of spheres, each one containing a magnetic dipole, rolling on a horizontally placed dish and subject to a magnetic field which is sinusoidal in time and spatially homogeneous. A gaslike state is obtained. Except for extremely low amplitudes of the magnetic field, non-Gaussian distributions are found for the translatory velocities, as well as for the horizontal components of the rotational velocities. However, the vertical component of the rotational velocity obeys an almost invariant Gaussian distribution within a large range of parameters, namely frequencies and amplitudes of the magnetic field and friction coefficients on the dish's bottom. The results are close to predictions from simulations by Cafiero [Europhys. Lett. 60, 854 (2002)].
我们通过实验研究了一种均匀驱动的颗粒介质。它由球体组成，每个球体都包含一个磁偶极子，在水平放置的盘子上滚动，并受到一个随时间呈正弦变化且空间均匀的磁场作用。我们得到了一种类似气体的状态。除了磁场幅度极低的情况外，平动速度以及转动速度的水平分量都呈现出非高斯分布。然而，在磁场的频率、幅度以及盘子底部的摩擦系数等参数的很大范围内，转动速度的垂直分量都服从几乎不变的高斯分布。这些结果与卡菲罗的模拟预测[《欧洲物理快报》60, 854 (2002)]相近。
