Electrorheological effect and directional non-Newtonian behavior in a nematic capillary subjected to a pressure gradient

Abstract

We consider a capillary consisting of two coaxial cylinders whose core is filled with a nematic liquid crystal (LC) subjected to the simultaneous action of both a pressure gradient applied parallel to the axis of the cylinders and a radial low frequency electric field. We find the configuration of the director of the nematic, initially with an escaped-like configuration, for the flow aligning LC 4'-n-pentyl-4-cyanobiphenyl (5CB) by assuming hard anchoring hybrid boundary conditions. Also, we obtain the velocity profile parametrized by the electric field and the pressure gradient for nonslip boundary conditions. Finally, we calculate exactly the effective viscosity, the first normal stress difference, and the dragging forces on the cylinders. The results show an important electrorheological effect and a directional non-Newtonian response with regions of flow thinning and thickening.