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Contact dynamics in a gently vibrated granular pile.
Alexandre Kabla1, Georges Debrégeas
1LFO-Collège de France, CNRS UMR 7125, Paris, France.
Physical Review Letters
|February 3, 2004
Summary
Gentle taps on granular piles increase the time between plastic events, mimicking aging in glassy systems. This microscopic dynamics is linked to evolving particle contact forces.
Area of Science:
- Granular physics
- Soft matter physics
- Complex systems
Background:
- Granular materials exhibit complex dynamics under external stimuli.
- Aging phenomena are typically observed in thermal glassy systems.
Purpose of the Study:
- To investigate the micron-scale dynamics of granular piles under tapping.
- To understand the mechanism behind the observed slowing-down dynamics.
- To draw parallels between granular aging and thermal glass aging.
Main Methods:
- Utilizing multispeckle diffusive wave spectroscopy (MS-DWS) to probe dynamics.
- Applying discrete gentle taps to a water-saturated granular pile.
- Analyzing the time scale of plastic events and its dependence on tapping and solid fraction.
Main Results:
- The time scale between plastic events significantly increases with the number of taps.
- Microscopic dynamics show weak dependence on the solid fraction of the granular sample.
- The observed behavior resembles the aging phenomenon in thermal glassy systems.
Conclusions:
- Granular aging under tapping is driven by a slow evolution of inter-particle contact forces.
- A heuristic model based on contact force distribution successfully explains the observed dynamics.
- The study highlights analogies between granular and thermal glassy systems.