Abstract
Chaotic mixing in a curved-square channel flow is studied experimentally and numerically. Two walls of the channel (inner and top walls) rotate around the center of curvature and a pressure gradient is imposed in the direction toward the exit of the channel. This flow is a kind of Taylor-Dean flows. 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 the present paper, we analyze the physical mechanism of chaotic mixing in the Taylor-Dean flow by comparing experimental and numerical results. We produced a micromixer model of the curved channel several centimeters long with square cross section of a few millimeters side. The secondary flow was measured using laser induced fluorescence (LIF) method to examine secondary flow characteristics. We also performed three-dimensional numerical simulations for the exactly same configuration as the experimental system to study the mechanism of chaotic mixing. It is found that good mixing performance is achieved for the case of De ≤ 0.1Tr, and that mixing efficiency changes according to the difference in inflow conditions. The flow is studied both experimentally and numerically, and both results agree with each other very well.
Highlights
Great attention has been paid to the development of a micro-chemical-analysis device called the microHow to cite this paper: 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
The flow is in the very low Reynolds number region because of the microsize of the channel, where mechanical mixing by turbulence cannot be expected without a special artifice
We proposed a micromixer making use of chaos of the secondary flow, a micromixer in which the secondary flow becomes chaotic through a curved channel where two walls of the channel rotate [6]
Summary
Great attention has been paid to the development of a micro-chemical-analysis device called the microHow to cite this paper: 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. This device, which consists of various microflow devices and sensors, functions through a series of operations such as mixture, reaction, separation, and extraction. The flow is in the very low Reynolds number region because of the microsize of the channel, where mechanical mixing by turbulence cannot be expected without a special artifice. A micromixer is needed to mix low-Reynolds-number flows efficiently. Stroock et al [1] studied a micromixer generating secondary flows in a channel by carving a ditch into the channel wall surface. Sato et al [3] made a micromixer that generates stronger secondary flows by carving ditches into the three wall surfaces of the channel. It has been shown that these methods are effective when the flow velocity is fast, the pressure loss becomes a serious problem in this case
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