The micromixer, which has a rotor with a curved channel, is studied experimentally. The secondary flow in a curved channel of square cross-section is investigated using PIV (Particle Image Velocimetry) and LIF (Laser Induced Fluorescence) method. 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 6 = aIR 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 = Re61/2, where Re = Q1(2av) is the Reynolds number, Q the flux, v the kinematic viscosity, and the Taylor number Tr = 2a2S2(26)1/2/(6v), where 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 achieved in the case of De < 0.11 Trl and for that case secondary flows show chaotic behaviors. And then we have confirmed the occurrence of reflux of main flow.
