A microfluidic rheometer for a non-Newtonian fluids based on the analysis of the recirculation angle of secondary flows in a U-shaped channel

The results of systematic computational and experimental studies on the flow modes of a non-Newtonian viscoplastic fluid in a U-shaped channel of a microfluidic viscometer are presented. The effect of flow rate and rheological parameters of the fluid on the flow structure and the Dean vortex behavior in the channel was investigated. It was shown that Dean vortices can occur in different regions of U-curvature, depending on certain parameters. The developed rheometer was demonstrated to be able to determine rheological parameters for non-Newtonian fluids. Moreover, this viscometer can be integrated directly into the flow without the need for fluid sampling for analysis. It has been shown that the following correlation can be used to find the flow behavior index and the consistency index: De−1(θ) = a (θ–c)b, where a = 10−4, b = 2, and c = 15. It was shown that the measurement error for this type of rheometer does not exceed 10%; however, it is necessary to measure the recirculation angle with high accuracy to avoid an increase in discrepancy.