Numerical simulation of different non-Newtonian fluids mixing with concentration dependent rheological properties in curved micromixers

A numerical study was conducted on the mixing of two different fluids in curved micromixers. The effect of mass flow rate and location of inlet fluids on mixing index were examined. The flow was assumed three dimensional, laminar, steady and incompressible. Also, the governing equations were solved using OpenFOAM open source CFD code. In order to simulate the mixing between two different fluids, viscosity parameters of power-law nonNewtonian fluid were considered as functions of concentration using some curve fittings. The results showed that the effect of location of inlet fluids on mixing index is effective when two different fluids with high mass fraction differences are being mixed. This means that the mixing index is higher when the fluid with low mass fraction rate enters from the near center inlet of curved channel. Also, the effect of location of inlet fluids on mixing index is dependent on geometry of micromixers. In other words, in geometry with high mixing quality, the effect of fluid location is negligible. Furthermore, the location of inlet fluids has no significant effects on the mixing index of two fluids with close mass fraction rates.