Numerical investigation of mixing performance in spiral micromixers based on Dean flows and chaotic advection

Abstract

In this work, we propose three innovative spiral micromixers viz., a simple spiral (SS) micromixer, SE micromixer designed by modifying the center part of the spiral one with straight walls, and RS micromixer designed by modifying the whole spiral part with straight walls. Numerical investigations are performed to analyze the strength of Dean vortices and chaotic advection, the mixing and pressure drop characteristics in the micromixers for Reynolds number (Re) in the range of 0.1 to 100 and for different depth and width of the mixers. It reveals that at Re=0.1, all the micromixers show almost similar mixing index and for 0.1<Re≤10 the mixing index decreases with Re. Further increasing Re beyond 10, the mixing index increases due to the formation of Dean vortices and chaotic advection. In SE and RS micromixers, 24% and 25% more mixing are obtained respectively than that of SS micromixer. The maximum pressure drop is observed in RS micromixer followed by SE and SS micromixers. The mixing performance representing the combined mixing index and pressure drop is maximum for SE micromixer among all three micromixers. The effect of change in width in altering the mixing index is more than that of the depth.