Chaotic mixing in three different types of curved-rectangular channels flow has been studied experimentally and numerically. Two walls of the channel (inner and top walls) rotate around the center of curvature and a pressure gradient are imposed in the direction toward the exit of the channel. This flow is a kind of Taylor-Dean flow. There are two parameters dominating the flow, the Dean number De (∝ the pressure gradient or the Reynolds number) and the Taylor number Tr (∝ the angular velocity of the wall rotation). In this paper, we analyze the physical mechanism of chaotic mixing in the Taylor-Dean flow by comparing experimental results and numerical ones. We produced three micromixer models of the curved channel, several centimeters long, with rectangular cross-section of a few millimeters side. The secondary flow is measured using laser induced fluorescence (LIF) method to examine secondary flow characteristics. Also we performed three-dimensional numerical simulations with the open source CFD solver, OpenFOAM, for the same configuration as the experimental system to study the mechanism of chaotic mixing. It is found that good mixing performance is obtained in the case of De ≤ 0.1 Tr, and it becomes more remarkable when the aspect ratio tends to large. And it is found that the mixing efficiency changes according to the aspect ratio and inflow condition.
Sato, H., Ito, S., Tajima, K., Orimoto, N. and Shoji, S. (2005) PDMS Microchannels with Slanted Grooves Embedded in Three Walls to Realize Efficient Spiral Flow. Sensors and Actuators A: Physical, 119, 365-371.
Tabeling, P., Chabert, M., Dodge, A., Jullien, C. and Okkels, F. (2004) Chaotic Mixing in Cross-Channel Micromixers. Philosophical Transactions of the Royal Society A, 362, 987-1000. http://dx.doi.org/10.1098/rsta.2003.1358
Xia, H.M., Wan, S.Y.M., Shu, C. and Chew, Y.T. (2005) Chaotic Micromixers Using Two-Layer Crossing Channels to Exhibit Fast Mixing at Low Reynolds Numbers. Lab on a Chip, 5, 748-755. http://dx.doi.org/10.1039/b502031j
Jang, B. and Funakoshi, M. (2010) Chaotic Mixing in a Helix-Like Pipe with Periodic Variations in Curvature and Torsion. Fluid Dynamics Research, 42, 1-24. http://dx.doi.org/10.1088/0169-5983/42/3/035506
Hayamizu, Y., Yanase, S., Morita, S., Ohtsuka, S., Gonda, T., Nishida, K. and Yamamoto, K. (2012) A Micromixer Using the Chaos of Secondary Flow: Rotation Effect of Channel on the Chaos of Secondary Flow. Open Journal of Fluid Dynamics, 2, 195-201. http://dx.doi.org/10.4236/ojfd.2012.24A021
Yamamoto, K., Wu, X.Y., Nozaki, K. and Hayamizu, Y. (2006) Visualization of Taylor-Dean Flow in a Curved Duct of Square Cross-Section. Fluid Dynamics Research, 38, 1-18. http://dx.doi.org/10.1016/j.fluiddyn.2005.09.002
Kawabe, T., Hayamizu, Y., Yanase, S., Gonda, T., Morita, S., Ohtsuka, S. and Yamamoto, K. (2014) A Micromixer Using the Taylor-Dean Flow: Effect of Inflow Conditions on the Mixing. Open Journal of Fluid Dynamics, 4, 463-471.
Hayamizu, Y., Yanase, S., Nishida, K. and Yamamoto, K. (2013) Chaotic Mixing in a Curved-Square Duct Flow at Very Low Reynolds Numbers. Journal of the Physical Society of Japan, 82, Article ID: 103401.