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Taylor dispersion in a pulsatile flow of a viscoelastic fluid through an eccentric annular tube

Published online by Cambridge University Press:  09 March 2026

Geraldy Covarrubias
Affiliation:
ESIME Azcapotzalco, Instituto Politécnico Nacional , Colonia Santa Catarina, Alcald´ıa Azcapotzalco, Ciudad de México 02250, Mexico
Oscar Bautista*
Affiliation:
ESIME Azcapotzalco, Instituto Politécnico Nacional , Colonia Santa Catarina, Alcald´ıa Azcapotzalco, Ciudad de México 02250, Mexico
José Arcos
Affiliation:
ESIME Azcapotzalco, Instituto Politécnico Nacional , Colonia Santa Catarina, Alcald´ıa Azcapotzalco, Ciudad de México 02250, Mexico
Federico Méndez
Affiliation:
Departamento de Termofluidos, Facultad de Ingeniería, Universidad Nacional Autónoma de México, Ciudad Universitaria, Alcaldía Coyoacán, 04510, Ciudad de México, Mexico
*
Corresponding author: Oscar Bautista, obautist1@gmail.com

Abstract

Taylor dispersion of a solute in a pulsatile flow of a viscoelastic fluid, whose constitutive equation follows the Maxwell model, through an eccentric annulus is investigated in this work. To determine the effective dispersion coefficient, $\mathscr{D}_{\textit{eff}}$, we have used the multiple-scale analysis in conjunction with the homogenization method. The governing equation describing this dispersive phenomenon for solute concentration is the advection-diffusion equation, which depends on the velocity profile. Therefore, the momentum equation must be solved in advance. A hyperbolic partial differential equation in a bipolar coordinate system was derived by combining the Cauchy momentum equation with Maxwell’s constitutive equation. Parameters such as the Womersley number, ${\textit{Wo}}$, and the Deborah number, ${\textit{De}}$, control the time-dependent flow and viscoelasticity, respectively. For low Womersley numbers, i.e. for low frequencies, an increase in the Deborah number, the eccentricity, $\phi$, and gap width, $\gamma$, leads to an enhancement of the effective dispersion coefficient. For instance, a fluid with ${\textit{De}} = 5$ could increase $\mathscr{D}_{\textit{eff}}$ by two orders of magnitude compared with a Newtonian fluid with the same settings ($\phi = 0.3$ and ${\textit{Wo}} = 0.1$). However, this enhancement due to the viscoelastic effect is only significant at low frequencies. An advection-diffusion equation for the mean concentration in the cross-section was also derived and evaluated in the same low-frequency limit. It was concluded that pulsatile flow maximises the axial dispersion compared with steady and purely oscillatory flows.

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Type
JFM Papers
Copyright
© The Author(s), 2026. Published by Cambridge University Press

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Supplementary material: File

Covarrubias et al. supplementary movie 1

Animation of the influence of eccentricity on the dispersion of the solute in a Newtonian fluid for different dimensionless times. For a pulsatile flow with ϵ = 0.001, γ = 5, g = 1 and Sc = 103.
Download Covarrubias et al. supplementary movie 1(File)
File 15.7 MB
Supplementary material: File

Covarrubias et al. supplementary movie 2

Animation of the viscoelastic influence on the dispersion of the solute for different dimensionless times. For a pulsatile flow with ϵ = 0.001, γ = 5, g = 1 and Sc = 103.
Download Covarrubias et al. supplementary movie 2(File)
File 18.7 MB
Supplementary material: File

Covarrubias et al. supplementary movie 3

Animation of the viscoelastic fluid under different flow conditions. For a flow with ϵ = 0.001, γ = 5, g = 1 and Sc = 103.
Download Covarrubias et al. supplementary movie 3(File)
File 14.2 MB
Supplementary material: File

Covarrubias et al. supplementary movie 4

Animation of the influence of Péclet number on mean concentration in a pulsatile flow for viscoelastic fluids. Considering ϵ = 0.001, γ = 5, g = 1 and Sc = 103.
Download Covarrubias et al. supplementary movie 4(File)
File 4.6 MB
Supplementary material: File

Covarrubias et al. supplementary movie 5

Animation of influence of Womersley number on mean concentration in a pulsatile flow for viscoelastic fluids. Considering ϵ = 0.001, γ = 5, g = 1 and Sc = 103.
Download Covarrubias et al. supplementary movie 5(File)
File 4.9 MB