Document Type

Article

Date

7-2-2011

Embargo Period

10-18-2011

Keywords

condensed matter, soft condensed matter

Language

English

Disciplines

Physics

Description/Abstract

Using minimal models for low Reynolds number passive and active rotors in a fluid, we characterize the hydrodynamic interactions among rotors and the resulting dynamics of a pair of interacting rotors. This allows us to treat in a common framework passive or externally driven rotors, such as magnetic colloids driven by a rotating magnetic field, and active or internally driven rotors, such as sperm cells confined at boundaries. The hydrodynamic interaction of passive rotors contains an azimuthal component 1/r2 to dipolar order that can yield the recently discovered “cooperative self-propulsion” of a pair of rotors of opposite vorticity. While this interaction is identically zero for active rotors as a consequence of torque balance, we show that a 1/r4 azimuthal component of the interaction arises in active systems to octupolar order. Cooperative self-propulsion, although weaker, can therefore also occur for pairs of active rotors.

Additional Information

This manuscript is from arXiv.org, there is other information at http://arxiv.org/abs/1107.0347

Source

harvested from arXiv.org

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