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Pure axial flow of viscoelastic fluids in rectangular microchannels under combined effects of electro-osmosis and hydrodynamics

Reshadi, M ; Sharif University of Technology | 2018

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  1. Type of Document: Article
  2. DOI: 10.1007/s00162-017-0428-y
  3. Publisher: Springer New York LLC , 2018
  4. Abstract:
  5. This paper presents an analysis of the combined electro-osmotic and pressure-driven axial flows of viscoelastic fluids in a rectangular microchannel with arbitrary aspect ratios. The rheological behavior of the fluid is described by the complete form of Phan-Thien–Tanner (PTT) model with the Gordon–Schowalter convected derivative which covers the upper convected Maxwell, Johnson–Segalman and FENE-P models. Our numerical simulation is based on the computation of 2D Poisson–Boltzmann, Cauchy momentum and PTT constitutive equations. The solution of these governing nonlinear coupled set of equations is obtained by using the second-order central finite difference method in a non-uniform grid system and is verified against 1D analytical solution of the velocity profile with less than 0.06% relative error. Also, a parametric study is carried out to investigate the effect of channel aspect ratio (width to height), wall zeta potential and the Debye–Hückel parameter on 2D velocity profile, volumetric flow rate and the Poiseuille number in the mixed EO/PD flows of viscoelastic fluids with different Weissenberg numbers. Our results show that, for low channel aspect ratios, the previous 1D analytical models underestimate the velocity profile at the channel half-width centerline in the case of favorable pressure gradients and overestimate it in the case of adverse pressure gradients. The results reveal that the inapplicability of the Debye–Hückel approximation at high zeta potentials is more significant for higher Weissenberg number fluids. Also, it is found that, under the specified values of electrokinetic parameters, there is a threshold for velocity scale ratio in which the Poiseuille number is approximately independent of channel aspect ratio. © 2017, Springer-Verlag Berlin Heidelberg
  6. Keywords:
  7. Electro-osmosis ; Microfluidics ; PTT model ; Rectangular microchannels ; Viscoelastic fluids ; Axial flow ; Constitutive equations ; Electrolysis ; Electroosmosis ; Finite difference method ; Flow of fluids ; Microchannels ; Nonlinear equations ; Osmosis ; Velocity ; Viscoelasticity ; Zeta potential ; Adverse pressure gradient ; Central finite difference ; Electrokinetic parameters ; Favorable pressure gradients ; PTT models ; Upper convected maxwells ; Vis-coelastic fluids ; Aspect ratio ; Computer simulation ; Electrokinesis ; Hydrodynamics ; Numerical model ; Parameterization ; Pressure gradient ; Two-dimensional modeling ; Velocity profile ; Viscoelastic fluid
  8. Source: Theoretical and Computational Fluid Dynamics ; Volume 32, Issue 1 , 2018 ; 09354964 (ISSN)
  9. URL: https://link.springer.com/article/10.1007%2Fs00162-017-0428-y