Palanisamy Duraivelan, den Otter Wouter K
MultiScale Mechanics, Faculty of Engineering Technology and MESA+ Institute for Nanotechnology, University of Twente, P.O. Box 217, 7500 AE Enschede, The Netherlands.
J Chem Phys. 2020 Feb 21;152(7):074901. doi: 10.1063/1.5141527.
The interplay between Brownian colloidal particles and their suspending fluid is well understood since Einstein's seminal work of 1905: the fluid consists of atoms whose thermal motion gives rise to the Brownian motion of the colloids, while the colloids increase the viscosity of the suspension under shear. An alternative route to the viscosity, by exploring the thermal stress fluctuations in a quiescent fluid in the Green-Kubo formalism, however, reveals a marked inconsistency with the viscosity under shear. We show that an additional stress term, accounting for Brownian fluctuating stresslets and coupled to the Brownian forces by a generalized fluctuation-dissipation theorem, is required for the description of the stress and viscosity of a colloidal suspension. Whereas previous applications of the Green-Kubo method to colloidal systems were limited to the deterministic "thermodynamic" part of the stress, using other means to determine the remainder of the viscosity, the whole viscosity is now within the reach of equilibrium studies.
自1905年爱因斯坦的开创性工作以来，布朗胶体颗粒与其悬浮流体之间的相互作用已得到充分理解：流体由原子组成，其热运动导致胶体的布朗运动，而胶体在剪切作用下会增加悬浮液的粘度。然而，通过在格林 - 库博形式体系中探索静态流体中的热应力涨落来研究粘度的另一种途径，揭示出与剪切下的粘度存在明显不一致。我们表明，为了描述胶体悬浮液的应力和粘度，需要一个额外的应力项，该项考虑了布朗涨落应力子，并通过广义涨落 - 耗散定理与布朗力耦合。以前将格林 - 库博方法应用于胶体系统时，仅限于应力的确定性“热力学”部分，使用其他方法来确定粘度的其余部分，而现在整个粘度都可以通过平衡研究来确定。
