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

纳米复合材料加工微通道中多元流体的流动诱导结构分析

基本信息

批准号：
18560667
负责人：
YASUDA Kazunori
金额：
$ 2.2万
依托单位：
Osaka University
依托单位国家：
日本
项目类别：
Grant-in-Aid for Scientific Research (C)
财政年份：
2006
资助国家：
日本
起止时间：
2006 至 2007
项目状态：
已结题

来源：
https://kaken.nii.ac.jp/grant/KAKENHI-PROJECT-18560667/
关键词：
complex fluid micro flow flow around a circular obstacle birefringence orientation angle non-Newtonian fluid flow -induced structure elongational flow バクテリアセルロースコンポジット成形加工流動特性レオロジー特性流路内流れ

项目摘要

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.

在宽度为4 mm，深度为1 mm的小通道中，对聚合物溶液的流动诱导结构进行了定量估计。我们制作了一个原始的光学系统来测量测试液体的双折射，这对应于0.1 mm步长空间内高分辨率的结构变化。此外，我们还测量了流道内的速度分布。因此，在障碍物的上游，由于减速气流使分子取向在垂直于气流的方向上排列，流体颗粒向障碍物流动时分子取向程度减小。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与垂直于流动的方向对齐。另一方面，在障碍物的下游，由于拉长流动，流体向下游方向流动，分子取向程度变大。这些测量是在通道空间的一个非常小的区域进行的。接下来，我们测量了细菌纤维素纳米纤维悬浮液（BC流体）在流动中的流态和速度分布。水流在具有矩形截面和4:1收缩的通道中可视化。牛顿流体的速度分布为抛物线状流动，而BC流体的速度分布为柱塞状流动。由于BC流体具有剪切变稀的黏度，因此BC浓度越大，其速度分布越像塞柱。此外，我们还测量了收缩时可入角的涡旋增强。结果，BC流体中的涡流比牛顿流体中的涡流更大。这是因为BC流体具有较大的延伸粘度。