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Inertial focusing of non-neutrally buoyant spherical particles in curved microfluidic ducts

Published online by Cambridge University Press:  04 September 2020

Brendan Harding Open the ORCID record for Brendan Harding [Opens in a new window]  and
Yvonne M. Stokes Open the ORCID record for Yvonne M. Stokes [Opens in a new window]
Brendan Harding*
Affiliation:
School of Mathematical Sciences, The University of Adelaide, Adelaide, South Australia5005, Australia
Yvonne M. Stokes
Affiliation:
School of Mathematical Sciences, The University of Adelaide, Adelaide, South Australia5005, Australia
*
†Email address for correspondence: brendan.harding@adelaide.edu.au
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Abstract

We examine the effect of gravity and (rotational) inertia on the inertial focusing of spherical non-neutrally buoyant particles suspended in flow through curved microfluidic ducts. In the neutrally buoyant case, examined in Harding et al. (J. Fluid Mech., vol. 875, 2019, pp. 1–43), the gravitational contribution to the force on the particle is exactly zero and the net effect of centrifugal and centripetal forces (due to the motion around the curved duct) is negligible. Inertial lift force and drag from the secondary fluid flow vortices interact and lead to focusing behaviour which is sensitive to the bend radius of the device and the particle size (each measured relative to the height of the cross-section). In the case of non-neutrally buoyant particles the behaviour becomes more complex with the two additional perturbing forces. The gravitational force, relative to the inertial lift force, scales with the inverse square of the flow velocity, making it a potentially important factor for devices operating at low flow rates with a suspension of non-neutrally buoyant particles. In contrast, the net centripetal/centrifugal force scales with the inverse of the bend radius, similar to the drag force from the secondary flow. We examine how these forces perturb the stable equilibria within the cross-sectional plane to which neutrally buoyant particles ultimately migrate.

JFM classification

Micro-/Nano-fluid dynamics: Microfluidics Multiphase and Particle-laden Flows: Particle/fluid flow
Type
JFM Papers
Information
Journal of Fluid Mechanics , Volume 902 , 10 November 2020 , A4
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Copyright
© The Author(s), 2020. Published by Cambridge University Press

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References

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