The Electro-Elastic Instability of Viscoelastic Fluid in a Microchannel with Obstacles Under Heterogeneous Surface Potential

Abstract

In this paper, the Electro-elastic instability(EEI) of an Oldroyd-B fluids flow the microchannel with the obstacles and heterogenous surface charged is studied. The changes in fluid flow are presented by considering three different ranges of Weissenberg numbers(Wi), the expansion lengths \(\textrm{EL}\), and the asymmetric potential distributions. Under the combined effects of heterogeneous surface potential and elastic stresses, not only the vortices but also lip vortices are generated near the obstacles. At lower Weissenberg numbers, the stable and symmetric flow field is observed. As Wi increases, it is worth noting that the flow field becomes unstable and chaotic due to the enhanced electro-elastic instability. But the asymmetry of the velocity diminishes as \(Wi>10\). In addition, the presence of different vortex dynamics is observed as the Wi varies, such as the lip vortices, angular vortices, and oscillating lip vortices. Further, the flow of fluid at different expansion ratios is investigated. With the decrease of expansion lengths \(\textrm{EL}\), the backflow and asymmetry are reduced, the lip vortex disappears and then the angular vortex appears. Finally, by increasing the upper zeta potential \((\zeta _{\textrm{w}})\) of the obstacles, the mixing efficiency is improved. The research results may be helpful to the electrodynamic transport of viscoelastic fluids in porous media and the analysis of micromixers for industrial applications.