A Micromixer Using the Chaos of Secondary Flow: Rotation Effect of Channel on the Chaos of Secondary Flow

Yasutaka Hayamizu

doi:10.4236/ojfd.2012.224021

Abstract

The micromixer, which has a rotor with a curved channel, is studied experimentally. The secondary flow in a curved channel of rectangular cross-section is investigated using PIV (Particle Image Velocimetry) and LIF (Laser Induced Fluorescence) methods. Two walls of the channel (the inner and top walls) rotate around the center of curvature and a pressure gradient is imposed in the direction of the exit of the channel. The non-dimensional channel curvature δ=a/R is taken to be about 0.1, where 2a is the width of the channel, R the curvature radius of the channel. Other non-dimensional parameters concerned are the Dean number De=Reδ1/2, the Reynolds number Re=qdh/v, where q is the mean flow velocity in the channel axis direction, ν the kinematic viscosity, dh the hydraulic diameter of the channel, and the Taylor number Tr=2(2δ)1/2Ωa2/(δv), where Ω is the angular velocity of the rotor. Photographs of the flow in a cross-section at 180° downstream from the curved channel entrance are taken by changing the flux (De) at a constant rotational speed (Tr) of the channel walls. It is found that good mixing performance is obtained in the case of De≤0.1|Tr| and for that case secondary flows show chaotic behaviors. And then we have confirmed the occurrence of reversal of the mean axial flow.

Highlights

A great attention has been paid to the development of a micro-chemical-analysis device called μTAS (Micro Total Analysis Systems) in the field of the chemistry and biotechnology
Since a micromixer with comparatively simple shape among them can be made using the method of creating secondary flows within the channel, the study of the micromixer of this type is important in a practical use of μTAS
It has been shown that these methods are effective when the flow velocity is fast, though the pressure loss becomes a serious problem in this case

Summary

Introduction

A great attention has been paid to the development of a micro-chemical-analysis device called μTAS (Micro Total Analysis Systems) in the field of the chemistry and biotechnology This device, which consists of various micro-flow devices and sensors, functions in a series of operation such as mixture, reaction, separation and extraction. Since a micromixer with comparatively simple shape among them can be made using the method of creating secondary flows within the channel, the study of the micromixer of this type is important in a practical use of μTAS. Stroock et al [1] studied a micromixer generating secondary flows in a channel by carving a ditch on the channel wall surface. Sato et al [3] made a micromixer which generates stronger secondary flows by carving ditches on the three wall surfaces of the channel. We propose a micromixer making use of the chaos of the secondary flow, one in which the secondary flow becomes chaotic through a curved channel where two walls of the channel rotate

Methods

Results

Conclusion