Flow field disturbance due to point viscosity variations in a heterogeneous fluid

TL;DR

This paper derives the flow disturbance caused by point viscosity variations in a heterogeneous fluid, revealing how these variations influence the hydrodynamics of active particles and enabling their manipulation in microfluidics.

Contribution

It introduces a theoretical and numerical framework to understand and exploit viscosity-induced flow disturbances for controlling active particles.

Findings

Flow disturbance is equivalent to a force-dipole (stresslet).

Viscosity variations alter active particle hydrodynamics.

Potential for steering particles in microfluidic devices.

Abstract

We derive the flow field disturbance produced by point viscosity variations in a heterogeneous fluid when subject to a background flow while neglecting fluid inertia. The disturbance flow field is found to be identical to that generated by a force-dipole called stresslet. Using a combination of theory and numerical simulations, we show how the hydrodynamics of an active rigid particle is altered due to the presence of point viscosity variations, and how this can be exploited to manipulate and steer them in microfluidic environments.