Rotating electroosmotic flow of viscoplastic material between two parallel plates

• Published in: Colloids and surfaces. A, Physicochemical and engineering aspects Vol. 513; pp. 355 - 366
• Main Authors: Qi, Cheng, Ng, Chiu-On
• Format: Journal Article
• Language: English
• Published: Elsevier B.V 05.01.2017
• Subjects: Electric double layer; Electroosmotic flow; System rotation; Viscoplastic yield stress; Electroosmotic flow; Electric double layer; Viscoplastic yield stress; System rotation
• ISSN: 0927-7757; 1873-4359
• DOI: 10.1016/j.colsurfa.2016.10.066

This paper is to look into electroosmotic flow of a viscoplastic material, modeled as Bingham plastic or Casson fluid, through a parallel-plate channel that rotates about an axis perpendicular to the plates. To solve the problem, the yield surface, where the stress is equal in magnitude to the yield stress, has to be found simultaneously with the velocity and stress components in the sheared and unsheared regions. [Display omitted] •Electroosmotic (EO) flow of viscoplastic material in a rotating channel.•Viscoplastic material modeled as Bingham plastic and Casson fluid.•An iterative numerical scheme to solve the nonlinear problem.•Nonlinear interaction between yield stress and system rotation.•Rotating EO flow affected differently by the yield stress, depending on the viscoplastic model. This study aims to investigate electroosmotic flow of a viscoplastic material, modeled as either Bingham plastic or Casson fluid, through a parallel-plate channel that rotates about an axis perpendicular to the plates. A relatively small yield stress, comparable to that of human blood, is considered in order to confine to the condition there is only one yield surface in the flow. An iterative finite-difference numerical scheme is developed to solve the Cauchy momentum equations and nonlinear constitutive equations. The location of the yield surface, and velocity and stress components in both the sheared and unsheared regions are found as functions of the yield stress, rotation speed and Debye parameter. Numerical results are presented to reveal that the system rotation and yield stress may counteract each other in controlling the resultant flow rate and flow direction. The effect of yield stress may even be reversed for a sufficiently large rotation speed.