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Brownian Granular Flows Down Heaps
Antoine Bérut1, Olivier Pouliquen1, Yoël Forterre1
1Aix Marseille Univ, CNRS, IUSTI, Marseille 13013, France.
Physical Review Letters
|January 11, 2020
Summary
Granular avalanches in microfluidic drums exhibit unique behavior, flowing until horizontal rather than stopping at a fixed angle. This phenomenon is modeled using Kramers
Area of Science:
- Granular physics
- Soft matter physics
- Microfluidics
Background:
- Classical granular materials exhibit a finite angle of repose.
- Avalanche dynamics are typically studied in macroscopic systems.
Purpose of the Study:
- To investigate the avalanche dynamics of micrometer-sized silica grains in a microfluidic environment.
- To understand deviations from classical granular material behavior.
Main Methods:
- Experiments using water-filled microfluidic drums with silica grains.
- Observation of avalanche dynamics and pile relaxation.
- Development of a one-dimensional model based on Kramers' escape rate.
Main Results:
- Granular avalanches did not stop at a finite angle of repose.
- A rapid relaxation phase was followed by a logarithmic creep regime.
- Relaxation time depended on the gravitational Péclet number.
Conclusions:
- Brownian motion significantly influences granular avalanche dynamics at the microscale.
- A model based on Kramers' escape rate accurately describes the observed behavior.
- The study challenges classical granular mechanics assumptions in microfluidic settings.
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