Caldag, Hakan Osman orcid.org/0000-0002-4394-6045 and Bees, Martin Alan (Accepted: 2025) Fine-tuning the dispersion of active suspensions with oscillatory flows. Philosophical Transactions of the Royal Society A: Mathematical, Physical and Engineering Sciences. ISSN 1471-2962 (In Press)
Abstract
The combined impact of axial stretching and cross-stream diffusion on the downstream transport of solute is termed Taylor dispersion. The dispersion of active suspensions is qualitatively distinct: viscous and external torques can establish non-uniform concentration fields with weighted access to shear, modifying mean drift and effective diffusivity. It would be advantageous to fine-tune the dispersion for systems such as bioreactors, where mixing or particle separation can improve efficacy. Here, we investigate the dispersion of active suspensions in a vertical channel driven by an oscillatory pressure gradient - Womersley flow - using gyrotactic swimmers (bottom-heavy cells subject to viscous torques). Preliminary experimental results reveal interesting dispersion phenomena, highly dependent on the oscillation parameters, motivating theoretical investigation. Employing Lagrangian simulations, we find that oscillatory flows can induce drift and increase lateral and downstream dispersion, with periodic mixing between left and right sides. Such flows can also be used to separate species with different motile behaviour. Eulerian numerical schemes typically require an approach to averaging in orientational space, such as generalised Taylor dispersion, with assumptions on translational and rotational time scales. For an oscillatory timescale commensurate with cell dynamics, we reveal the limitations of such approximations, beyond which the averaging techniques collapse.
Metadata
Item Type: | Article |
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Authors/Creators: |
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Copyright, Publisher and Additional Information: | This is an author-produced version of the published paper. Uploaded in accordance with the University’s Research Publications and Open Access policy. |
Keywords: | pulsatile flows,biofluid mechanics,Taylor dispersion,active suspensions |
Dates: |
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Institution: | The University of York |
Academic Units: | The University of York > Faculty of Sciences (York) > Mathematics (York) |
Depositing User: | Pure (York) |
Date Deposited: | 23 May 2025 12:00 |
Last Modified: | 23 May 2025 12:00 |
Status: | In Press |
Refereed: | Yes |
Open Archives Initiative ID (OAI ID): | oai:eprints.whiterose.ac.uk:227063 |
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