Nordita, Royal Institute of Technology and Stockholm University, Stockholm 106 91, Sweden.
J Chem Phys. 2019 Jul 14;151(2):024107. doi: 10.1063/1.5096764.
It is intuitive that the diffusivity of an isolated particle differs from those in a monodisperse suspension, in which hydrodynamic interactions between the particles are operative. Batchelor [J. Fluid Mech. 74, 1-29 (1976) and J. Fluid Mech. 131, 155-175 (1983)] calculated how hydrodynamic interactions influenced the diffusivity of a dilute suspension of spherical particles, and Russel et al. [Colloidal Dispersions (Cambridge University Press, 1991)] and Brady [J. Fluid Mech. 272, 109-134 (1994)] treated nondilute (higher particle volume fraction) suspensions. Although most particles lack perfect sphericity, little is known about the effects of hydrodynamic interactions on the diffusivity of spheroidal particles, which are the simplest shapes that can be used to model anisotropic particles. Here, we calculate the effects of hydrodynamic interactions on the translational and rotational diffusivities of spheroidal particles of arbitrary aspect ratio in dilute monodisperse suspensions. We find that the translational and rotational diffusivities of prolate spheroids are more sensitive to eccentricity than for oblate spheroids. The origin of the hydrodynamic anisotropy is that found in the stresslet field for the induced-dipole interaction. However, in the dilute limit, the effects of anisotropy are at the level of a few percent. These effects have influence on a vast range of settings, from partially frozen colloidal suspensions to the dynamics of cytoplasm.
显然，孤立粒子的扩散系数与处于单分散悬浮液中的扩散系数不同，在单分散悬浮液中，粒子之间存在流体动力相互作用。Batchelor [J. Fluid Mech. 74, 1-29 (1976) and J. Fluid Mech. 131, 155-175 (1983)] 计算了流体动力相互作用如何影响稀释悬浮液中球形粒子的扩散系数，Russel 等人 [Colloidal Dispersions (Cambridge University Press, 1991)] 和 Brady [J. Fluid Mech. 272, 109-134 (1994)] 处理了非稀释（更高的粒子体积分数）悬浮液。尽管大多数粒子缺乏完美的球形，但对于流体动力相互作用对各向异性粒子的球形粒子扩散系数的影响知之甚少，而各向异性粒子的最简单形状可以用来模拟各向异性粒子。在这里，我们计算了在单分散稀释悬浮液中任意纵横比的椭球粒子的流体动力相互作用对平移和旋转扩散系数的影响。我们发现，长轴比为扁球体的平移和旋转扩散系数对偏心率比扁球体更敏感。流体动力各向异性的起源是诱导偶极相互作用的应力张量场中发现的。然而，在稀相极限下，各向异性的影响处于百分之几的水平。这些影响对从部分冻结的胶体悬浮液到细胞质动力学等广泛的环境都有影响。
