Effects of Electroosmosis Flow of Bingham Plastic Fluid Induced by a Curved Microtube

Abstract

This paper investigates the pressure-driven and electroosmotic flow of Bingham plastic fluid within a curved microtube in the presence of a streaming potential. Perturbation analysis is utilised to solve the governing equations and obtain approximate analytical solutions. Validation against existing literature confirms the accuracy of the approach, with highly favourable agreement observed. The electrical double-layer (EDL) distribution is analysed for various Debye lengths, perturbation parameters, curvature ratios, and zeta potentials. As curvature increases, the EDL decreases near the lower wall and increases near the upper wall. The impact of electroosmosis force, Debye lengths, perturbation parameters, curvature ratios, and ionic Peclet number on axial velocity profiles is investigated. Axial velocity increases with the electroosmotic parameter value due to a more significant axial electric force in the inner area. Additionally, velocity decreases with increasing Bingham parameter, particularly at the lower wall region, while it increases with curvature value in the upper half of the tube. Higher flow rates are observed within curved microtubes than linear ones under similar pressure gradients and cross-sectional shapes. Increasing Debye length reduces streaming potential magnitude, favouring pressure-driven flow over electroosmotic flow. Finally, the variation of electrokinetic energy conversion efficiency with curvature ratio for different Bingham parameters is analysed. Higher Bingham parameter values increase fluid viscosity, resulting in slower fluid movement, reduced streaming potential, and decreased efficiency of electrokinetic energy conversion. This study contributes to a deeper understanding of fluid dynamics within curved microtubes and offers insights into optimising energy conversion efficiency in Bingham plastic fluid systems.