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arXiv · 1705.05978

Kinematic irreversibility in surfactant-laden interfaces

Harishankar Manikantan·Todd M. Squires
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Abstract

The surface shear viscosity of an insoluble surfactant monolayer often depends strongly on its surface pressure. Here, we show that a particle moving within a bounded monolayer breaks the kinematic reversibility of low-Reynolds-number flows. The Lorentz reciprocal theorem allows such irreversibilities to be computed without solving the full nonlinear equations, giving the leading-order contribution of surface-pressure-dependent surface viscosity. In particular, we show that a disk translating or rotating near an interfacial boundary experiences a force in the direction perpendicular to that boundary. In unbounded monolayers, coupled modes of motion can also lead to non-intuitive trajectories, which we illustrate using an interfacial analog of the Magnus effect. This perturbative approach can be extended to more complex geometries, and to 2D suspensions more generally.

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Harishankar Manikantan, Todd M. Squires. 2017-05-17. Kinematic irreversibility in surfactant-laden interfaces. https://doi.org/10.1098/rspa.2017.0346

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