Velocity measurement of velocity profile of complex fluids through a microchannel and the effect of the channel size on the flow pattern

复杂流体通过微通道的速度分布的速度测量以及通道尺寸对流型的影响

• 批准号: 15560141
• 负责人: YASUDA Kazunori
• 金额: $ 2.37万
• 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: 2003
• 资助国家: 日本
• 起止时间: 2003 至 2004
• 项目状态: 已结题
• 来源: https://kaken.nii.ac.jp/en/grant/KAKENHI-PROJECT-15560141/
• 关键词: Microchannel; Flow visualization; Complex fluid; Microstructure; Wall slip; Velocity profile; サイズ効果

Flows of polymer solutions through a 3.71 abrupt contraction were observed in a micro- and a regular-size channels. The test fluids are 0.2 wt% aqueous solutions of polyacrylamide whose molecular weights are 6×10^6 (fluid A), 1.5×10^7 (fluid B), and 1.9×10^7 (fluid C). The microchannel was made of PDMS and it is mounted on the glass plate. The growth of the salient corner vortex is discussed as a function of the shear rate, the Weissenberg number We and the viscoelastic Mach number M. Consequently, for the flows of fluid B and C, the vortex size in the microchannel is smaller than that in the regular-size one. The vortex grows with increasing the shear rate, We and M, but more quickly through the microchannel compared with the results in the regular-size one. However, the difference of tendency of the vortex enhancement between flows in the micro-size and the regular-size channels was not observed for the fluid A. Velocity profiles of polymer solutions were directly measured. The velocity profile in the depth direction is discussed as a function of the flow rate and shear stress on the wall. Consequently, for the flows of fluid A, a symmetric profile is observed in the region between the PDMS wall and the glass wall in a low flow rate, but the velocity profile slightly becomes asymmetric with increasing the flow rate : the velocity near the PDMS wall is larger than that near the glass wall. For the flows of fluid B, a slightly asymmetric profile is observed even in the low flow rate and a largely asymmetric one in the large flow rate. This large apparent slip on the PDMS wall significantly affects the velocity profile in the flow of polymer solution through a PDMS microchip.

在微型和常规大小的通道中观察到通过3.71突然收缩的聚合物溶液的流动。测试液为0.2 wt％的聚丙烯酰胺水溶液，其分子量为6×10^6（流体A），1.5×10^7（流体B）和1.9×10^7（液体C）。微通道由PDM制成，并安装在玻璃板上。讨论了显着角涡流的生长，这是剪切速率，魏森贝格数量和粘弹性马赫数的函数。因此，对于流体B和C的流量，微通道中的涡流大小小于常规尺寸的涡流。与常规尺寸的结果相比，涡旋随着剪切速率的增加而增长，但通过微通道的速度更快。然而，对于流体A的流量和常规尺寸通道之间的涡流增强趋势差异。对于流体A。聚合物溶液的速度曲线是直接测量的。在深度方向上的速度曲线是作为流速和壁上剪切应力的函数讨论的。因此，对于流体A的流动，在PDMS壁和玻璃壁之间的区域中观察到对称曲线的流量低，但是随着流速的增加，速度曲线略有不对称：PDMS壁附近的速度比玻璃壁附近的速度大。对于流体B的流动，即使在低流速和大流量中，也观察到略有不对称的轮廓。 PDMS壁上的这种较大的明显滑动显着影响聚合物溶液通过PDMS微芯片的速度曲线。