Mixing Characteristics in a Serpentine Micro-Channel

Mixing characteristics in a 2D serpentine micro-channel were studied experimentally to understand the role of Dean vortices in enhancing mixing. Mixing plane deformation was visualized at Reynolds numbers ranging from 1 to 200 with the corresponding Dean numbers ranging from 1 to 205. The 2D serpentine micro-channel was found to be a poor mixer for Re<50 even though a strong presence of Dean vortices was observed. The generation of flow separated regions at sharp corners, above Re=100, was observed to cause a sharp increase in the mixing obtained. The interaction between the Dean vortices and the corner vortices was studied by imaging pathlines at varying depths near the sharp corners. The interaction produced rapid stretching and folding of the two fluids, which was determined to be the reason for the increased mixing at Re>100. This study will have a significant impact on the understanding of transport properties of flows in similar geometries.