Bivariant species mixing and pressure drop within a hybrid periodic modulated microslit

Abstract

In this article, a mathematical study is presented on electroosmotic flow (EOF) of power law fluids driven by an external electric field, where the heterogeneity of a microslit is created by multiple wavy triangular modulated polarized wall hurdles. The primary aim of this paper is to demonstrate and depict the mixing performance that generating more retention time and enhancing the interface area, which is evaluated both analytically and computationally. EOF in microchannels is restricted to low Reynolds numbers with a relatively high viscosity effect, which could predict advection domination in flow mixing due to heterogeneities that can supersede the need of flow turbulence. The numerical experiment is performed for the flow phenomena of this novel alternating microgrooves' patterning to generate an intensively transverse flow field, which represents strong reverse flow due to a higher pressure drop. The geometry modification and potential heterogeneity are the key factors to disturb the flow stream by fluid folding and stretching, leading to significant improvement in mixing efficiency. The numerical computations are performed for the nonlinear coupled Nernst–Planck–Navier Stokes equations using a control volume approach over a staggered grid algorithm to elaborate the performance of the electric potential distribution, the external electric field, the flow field, and the species concentration, which are the major contributors of the mixing efficiency. The evaluated results confirm that surface modulation substantially reduces the mass flow rate, effectively resulting in an increase in the retention time of the flow diffusion, which is justified through analytical testing. The nonlinear coupling effects are found to be more pronounced for shear thickening fluids rather than shear thinning and Newtonian solutions, resulting in a low torque corresponding to equilibrium conditions. To achieve a targeted mixing performance, it is observed that flow behavior indices should be optimized in terms of aversion of flow behavior index, viscous dissipation, and yield stress effect.