Worby William Kai Alexander, Nakamine Kento, Yokoyama Yuto, Muto Masakazu, Tagawa Yoshiyuki
Department of Mechanical Systems Engineering, Tokyo University of Agriculture and Technology, Koganei, Tokyo, 184-8588, Japan.
Micro/Bio/Nanofluidics Unit, Okinawa Institute of Science and Technology Graduate University, Kunigami-gun, Okinawa, 904-0495, Japan.
Sci Rep. 2024 Sep 20;14(1):21931. doi: 10.1038/s41598-024-73087-3.
In this study, the concept of rheo-optics was applied to explore the flow birefringence induced by the stress components along the camera's optical axis since it is often overlooked in the traditional theories of photoelastic flow measurement. A novel aspect of this research is that it involved conducting polarization measurements on simple shear flows, specifically from a perspective in which a shear-velocity gradient exists along the camera's optical axis. A parallel-plate-type rheometer and a polarization camera are employed for these systematic measurements. The experimental findings for dilute aqueous cellulose nanocrystal suspensions demonstrate that the flow birefringence can be expressed as a power law based on the power of the second invariant of the deformation-rate tensor. This suggests that flow birefringence can be universally characterized by the coordinate-independent invariants and a pre-factor determined by the direction of polarization measurement. By adjusting the nonlinear term in the stress-optic law, its applicability could be expanded to include three-dimensional fluid stress fields in which the stress is distributed along the camera's optical axis.
在本研究中，流变光学的概念被应用于探索由沿相机光轴的应力分量引起的流动双折射，因为它在传统的光弹性流动测量理论中常常被忽视。本研究的一个新颖之处在于，它涉及对简单剪切流进行偏振测量，特别是从沿相机光轴存在剪切速度梯度的角度进行测量。使用平行板型流变仪和偏振相机进行这些系统测量。稀水性纤维素纳米晶体悬浮液的实验结果表明，流动双折射可以表示为基于变形率张量第二不变量幂次的幂律。这表明流动双折射可以由与坐标无关的不变量和由偏振测量方向确定的前置因子普遍表征。通过调整应力 - 光学定律中的非线性项，其适用性可以扩展到包括应力沿相机光轴分布的三维流体应力场。
