Numerical simulation of fluid mixing in the ribbed microchannels

Micromixers have received much interest as essential part of microfluidic devices. Therefore, enhancement of mixing quality has gained a lot of attention in recent years. In the present study, improvement of mixing quality for two different miscible liquids is considered in passive micromixers. Numerical approach is based on a second order finite volume Jameson scheme in order to solve two dimensional incompressible Navier-Stocks and mass transport equations by implementing artificial compressibility. Mixing quality is influenced by Reynolds and Schmitt numbers as well as size and location of the ribs. Diffusion mechanism has the main role for mixing in micro scale fluid flows; therefore, increasing Peclet number leads to extend mixing time. In order to enhance mixing quality, ribs are used in different locations through the microchannel which cause more instability in the fluid flow and leads to a better mixing. The Reynolds number is constant while the Schmitt number is in the range of 10 to 100. However, in order to laminar fluid flow, ribs just have an influence near itself and faraway, mixing mechanism return to earlier state. Therefore, in low Reynolds numbers they have no effective influence. When Reynolds number increase, flow instability that is created by different ribs leads to a better mixing.