Flow characteristics and mixing performance of electrokinetically driven non-Newtonian fluid in contraction-expansion microchannel

A numerical investigation is performed into the flow characteristics and mixing performance of electrokinetically driven non-Newtonian fluid in a contraction-expansion microchannel. In the study, the rheological behavior of the fluid is characterized using a power-law model. The results show that the volumetric flow rate reduces as the flow behavior index increases, and thus an improved mixing performance is obtained. Furthermore, it is shown that for all considered values of the flow behavior index, the mixing performance can be enhanced by increasing the ratio of the main channel width to the contraction channel width, extending the length of the contraction channel, assigning a smaller value to the nondimensional Debye-Hückel parameter, and applying an appropriate electric field strength. Finally, it is shown that although the mixing efficiency reduces with a reducing flow behavior index, an acceptable mixing performance can still be obtained given an appropriate specification of the flow conditions and geometry parameters.