Exploring Dean flow induced mixing performance of shear‐thinning fluids in spiral micromixers

Abstract Computational fluid dynamics‐based investigations have been performed to explore the mixing characteristics of shear‐thinning power‐law fluids in a spiral micromixer. The investigation aims to understand the combined influence of rheology and flow conditions on mixing performance. The power‐law fluids with power‐law indices ( n ) ranging from 0.49 to 1 and Reynolds numbers (Re) from 1 to 150 are studied for the analysis. The study confirms that the swirling motion resulting from the formation of Dean vortices in the curved sections is the primary mechanism for enhancing mixing. As Re increases, the mixing index ( η ) first decreases and then increases, and the pressure drop (PD) increases irrespective of n . As the power‐law index ( n ) increases, the value of η increases accompanied with an increased pressure drop because of the increased apparent viscosity and related flow resistance. However, the effect of apparent viscosity overshadows at higher Reynolds numbers, resulting in a relatively higher mixing rate of fluids inside the spiral micromixer for fluids having a lower power‐law index. This work offers design suggestions for effective micromixer applications in biochemical and lab‐on‐a‐chip systems, as well as quantitative insight into how rheological behaviour affects Dean flow mixing.