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.
Original language | English (US) |
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Article number | 092301 |
Journal | Physical Review Fluids |
Volume | 2 |
Issue number | 9 |
DOIs | |
State | Published - Sep 2017 |
Funding
This work was supported primarily by the Gordon and Betty Moore Foundation through Grant No. GBMF3849 and the Materials Research Science and Engineering Center (MRSEC) program of the National Science Foundation under Award No. DMR-1420073. P.C. was partially supported by the Center for Bio-Inspired Energy Science, a DOE BES EFRC under Award No. DE-SC0000989. A.D. and B.D. were supported in part by the National Science Foundation under Award No. DMS-1418706. We gratefully acknowledge the support of NVIDIA Corporation with the donation of GPU hardware for performing some of the simulations reported here.
ASJC Scopus subject areas
- Computational Mechanics
- Modeling and Simulation
- Fluid Flow and Transfer Processes