On a suspension of nearly spherical colloidal particles under large-amplitude oscillatory shear flow
On a suspension of nearly spherical colloidal particles under large-amplitude oscillatory shear flow
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大振幅振荡剪切流下近球形胶体颗粒悬浮液的研究
DOI：
10.1017/jfm.2016.77
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发表时间：
2016
影响因子：
3.7
通讯作者：
Aditya S. Khair
中科院分区：
文献类型：
--
作者：
Aditya S. Khair
作为复杂流体的大振幅振荡剪切(LAOS)流变学的范例，定量了在振荡简单剪切流中经历布朗旋转的近球形颗粒的稀释单分散悬浮液的动力学。我们关注老挝的“强非线性”区域，由$it\beta和$it\beta//it\pha定义，其中$it\beta$是无量纲剪切率(或Weissenberg数)，${it\α}$是无量纲振荡频率(或Deborah数)。我们给出了粒子长时间周期取向概率密度函数的渐近解。我们的分析表明，取向动力学由快速振荡的“核心”区域(在剪切率幅度的倒数的时间尺度上)组成，当施加的流动消失时，这些“核心”区域被相对较短的缓慢演化的“转向”区域分开。然后建立了悬浮体剪应力和法向应力差(NSD)的一致有效近似：第一个NSD和第二个NSD对剪应力的非牛顿贡献分别衰减为$it\beta^^{-3/2}$，${it\beta}^{-1}$和$it\beta^^{-1/2}$。这些应力标度来源于转向区的取向动力学。因此，正是流动消失的时刻主导了老挝地下这种聚集型复杂流体的流变性。
The dynamics of a dilute, monodisperse suspension of nearly spherical particles that undergo Brownian rotations in an oscillatory simple shear flow is quantified, as a paradigm for large-amplitude oscillatory shear (LAOS) rheology of complex fluids. We focus on the ‘strongly nonlinear’ regime of LAOS, defined by ${\it\beta}\gg 1$ and ${\it\beta}/{\it\alpha}\gg 1$ , where ${\it\beta}$ is a dimensionless shear rate (or Weissenberg number) and ${\it\alpha}$ is a dimensionless oscillation frequency (or Deborah number). We derive an asymptotic solution for the long-time periodic orientation probability density function of the particles. Our analysis reveals that the orientation dynamics consists of ‘core’ regions of rapid oscillation (on the time scale of the inverse of the shear-rate amplitude), separated by comparatively short ‘turning’ regions of slow evolution when the imposed flow vanishes. Uniformly valid approximations to the shear stress and normal stress differences (NSDs) of the suspension are then constructed: the non-Newtonian contribution to the shear stress, first NSD and second NSD, decays as ${\it\beta}^{-3/2}$ , ${\it\beta}^{-1}$ and ${\it\beta}^{-1/2}$ , respectively, at large ${\it\beta}$ . These stress scalings originate from the orientation dynamics at the turning regions. Therefore, it is the occasions when the flow vanishes that dominate the rheology of this paradigmatic complex fluid under LAOS.
剪切流对单个轴对称颗粒旋转扩散的影响
影响因子：
3.7
作者：
Leahy, Brian D.;Koch, Donald L.;Cohen, Itai
通讯作者：
Cohen, Itai