Similarities and differences in the nonlinear flow behavior of simple and of molecular liquids
Similarities and differences in the nonlinear flow behavior of simple and of molecular liquids
复制标题
简单液体和分子液体非线性流动行为的异同
DOI：
10.1016/0378-4371(83)90178-4
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发表时间：
1983
期刊：
影响因子：
--
通讯作者：
S. Hess
中科院分区：
文献类型：
--
作者：
S. Hess
在介绍了描述非牛顿流动特性的粘性系数和平面Couette对称中的法向压差之后，提出了计算这些系数的方法，并对与线性粘弹性的联系作了一些评论。非线性流动行为源于流场的涡度和对称无痕剪切速率张量对分子分布函数的主要剪切速率诱导各向异性的影响。在分子液体的情况下，分子轴的取向分布（排列）是最相关的量;在简单液体中，它是对相关函数。结果可以推断从一个扩展版本的不可逆热力学的分子液体，从福克-普朗克方程的方法和简单的液体，从动力学方程的Kirkwood-Smoluchowski型的对相关函数。最后，一些修改进行了讨论，导致非解析剪切速率和频率的依赖性，在计算机模拟中观察到的粘度系数。
After the introduction of viscosity coefficients describing the non-Newtonian flow behavior and the normal pressure differences in a plane Couette symmetry, methods for the calculation of these coefficients are presented and some remarks on the connection with the linear viscoelasticity are made. The nonlinear flow behavior stems from the influence of the vorticity of the flow field and of the symmetric traceless shear rate tensor on the primary shear-rate-induced anisotropy of molecular distribution functions. In the case of molecular liquids the orientational distribution of the molecular axes (alignment) is the most relevant quantity; in simple liquids it is the pair-correlation function. Results are presented which can be inferred from an extended version of irreversible thermodynamics of molecular liquids; from a Fokker-Planck equation approach and for simple liquids, from a kinetic equation of Kirkwood-Smoluchowski type for the pair-correlation function. Finally, some modifications are discussed which lead to a nonanalytic shear-rate and frequency dependence as observed for the viscosity coefficients in the computer simulations.