Analysis of flow-induced structure of polynieric fluid in a miatchannel for processing of nano composite materials

在宽4mm、深1mm的小通道中，围绕一个小的圆形障碍物，定量地估计了聚合物溶液的流动诱导结构。我们制作了一个新颖的光学系统来测量测试液体的双折射，这对应于在0.1 mm步长的空间内以高分辨率的结构变化。此外，我们还测量了流道中的速度分布。结果，在障碍物的上游，分子取向的程度随着流体颗粒朝向障碍物流动而降低，因为分子取向由于减速流动而在垂直于流动的方向上排列。然而，就在障碍物的上游，分子取向的程度变得很大，因为取向几乎完美地在垂直于流动的方向上对齐。另一方面，在障碍物的下游，分子取向度随着流体由于伸长流动而沿下游方向流动而变大。这些测量是在通道空间中的非常小的区域内进行的。接下来，我们测量了由细菌纤维素制成的纳米纤维悬浮液（BC流体）的流动模式和速度分布。流动在具有矩形横截面和4：1收缩的通道中可视化。牛顿流体的速度剖面呈抛物线状，而BC流体的速度剖面呈塞状。由于BC流体具有剪切变稀的粘度，BC浓度越大，速度剖面越呈塞状。此外，我们还测量了收缩时凹角处的涡增强。结果，BC流体中的涡旋变得比牛顿流体中的涡旋大。这是因为BC流体具有大的拉伸粘度。

Flow-induced structure of polymer solutions has been estimated quantitatively around a small circular obstacle in a small channel, which has a 4 mm width and 1 mm depth. We made an original optical system to measure the birefringence of the test liquid, which corresponds to the change of the structure at a high resolution in a space of 0.1 mm step. Furthermore, we measured velocity distributions in the flow channel. As a result, in the upstream of the obstacle, the degree of molecular orientation decreases as the fluid particle flows towards the obstacle because the molecular orientation is aligned in the direction perpendicular to the flow due to the decelerating flow. Just upstream the obstacle, however, the degree of molecular orientation became large because the orientation is almost perfectly aligned in the direction perpendicular to the flow. On the other hand, in the downstream of the obstacle, the degree of molecular orientation became large as the fluid flows in the direction of the downstream due to the elongational flow. These measurements were carried out in a very small region in a channel space.Next, we measured the flow pattern and the velocity distribution in the flow of nano fiber suspension made of bacteria cellulose (BC fluid). The flow was visualized in the channel having rectangular cross section and a 4: 1 contraction. The velocity profile of the Newtonian fluid had a parabolic-like flow, but a plug-like flow in a BC fluid. The larger concentration of the BC became more plug-like velocity profile, because the BC fluid has a shear-thinning viscosity. Furthermore, we measured the vortex enhancement in the reentrant corner at the contraction. As a result, the vortex in the BC fluid became larger than that in a Newtonian fluid. This is because the BC fluid has a large elongational viscosity.