Tapia-Ignacio C, Moctezuma R E, Donado F, Weeks Eric R
Instituto de Ciencias Básicas e Ingeniería, Universidad Autónoma del Estado de Hidalgo, Mineral de la Reforma 42184, Hidalgo, México.
CONACYT-Instituto de Física "Manuel Sandoval Vallarta", Universidad Autónoma de San Luis Potosí, Alvaro Obregón 64, 78000 San Luis Potosí, S.L.P., México.
Phys Rev E. 2020 Aug;102(2-1):022902. doi: 10.1103/PhysRevE.102.022902.
We study the Brownian motion of ellipsoidal particles lying on an agitated granular bath composed of magnetic particles. We quantify the mobility of different floating ellipsoidal particles using the mean-square displacement and the mean-square angular displacement, and relate the diffusion coefficients to the bath particle motion. In terms of the particle major radius R, we find the translational diffusion coefficient scales roughly as 1/R^{2} and the rotational diffusion coefficient scales as roughly 1/R^{4}; this is consistent with the assumption that diffusion arises from random kicks of the bath particles underneath the floating particle. By varying the magnetic forcing, the bath particles' diffusivity changes by a factor of ten; over this range, the translational and rotational diffusion of the floating particles change by a factor of 50. However, the ratio of the two diffusion constants for the floating particles is forcing-independent. Unusual aspects of the floating particle motion include non-Gaussian statistics for their displacements.
我们研究了位于由磁性颗粒组成的搅拌颗粒浴上的椭球形颗粒的布朗运动。我们使用均方位移和均方角位移来量化不同漂浮椭球形颗粒的迁移率，并将扩散系数与浴颗粒运动联系起来。就颗粒的主半径(R)而言，我们发现平动扩散系数大致按(1/R^{2})缩放，转动扩散系数大致按(1/R^{4})缩放；这与扩散源于漂浮颗粒下方浴颗粒的随机碰撞这一假设一致。通过改变磁驱动力，浴颗粒的扩散率变化了一个数量级；在此范围内，漂浮颗粒的平动和转动扩散变化了50倍。然而，漂浮颗粒的两个扩散常数之比与驱动力无关。漂浮颗粒运动的不寻常之处包括其位移的非高斯统计特性。
