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arXiv · 1702.03350

Hydrodynamic shocks in microroller suspensions

Blaise Delmotte·Michelle Driscoll·Paul Chaikin·Aleksandar Donev
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Abstract

We combine experiments, large scale simulations and continuum models to study the emergence of coherent structures in a suspension of magnetically driven microrollers sedimented near a floor. Collective hydrodynamic effects are predominant in this system, leading to strong density-velocity coupling. We characterize a uniform suspension and show that density waves propagate freely in all directions in a dispersive fashion. When sharp density gradients are introduced in the suspension, we observe the formation of a shock. Unlike Burgers' shock-like structures observed in other active and driven confined hydrodynamic systems, the shock front in our system has a well-defined finite width and moves rapidly compared to the mean suspension velocity. We introduce a continuum model demonstrating that the finite width of the front is due to far-field nonlocal hydrodynamic interactions and governed by a geometric parameter: the average particle height above the floor.

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Blaise Delmotte, Michelle Driscoll, Paul Chaikin, Aleksandar Donev. 2017-02-10. Hydrodynamic shocks in microroller suspensions. https://arxiv.org/abs/1702.03350

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