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Hydrodynamic shocks in microroller suspensions

Blaise Delmotte*

Michelle Driscoll†

Paul Chaikin‡

Aleksandar Donev§

  • Courant Institute of Mathematical Sciences, New York University, New York, New York 10012, USA

  • Department of Physics, New York University, New York, New York 10003, USA

  • Department of Physics, New York University, New York, New York 10003, USA

  • Courant Institute of Mathematical Sciences, New York University, New York, New York 10012, USA

  • *delmotte@courant.nyu.edu
  • †mdriscoll@nyu.edu
  • ‡chaikin@nyu.edu
  • §donev@courant.nyu.edu
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Phys. Rev. Fluids 2, 092301(R) – Published 19 September, 2017

DOI: https://doi.org/10.1103/PhysRevFluids.2.092301

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' shocklike 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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References (31)

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Outline

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Phys. Rev. Fluids 2, 092301(R)– Published 19 September, 2017
  • Received 10 February 2017
Article part of CHORUS

©2017 American Physical Society

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