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Dynamics in vibrofluidized beds: A diffusing wave spectroscopy study
Marlo Kunzner1, Christopher Mayo1, Matthias Sperl1,2
1Deutsches Zentrum für Luftund Raumfahrt (DLR), Institut für Materialphysik im Weltraum, 51170 Cologne, Germany.
Physical Review. E
|September 16, 2025
Summary
Shaking granular systems densifies them over time, as shown by mean-square displacement (MSD) measurements. This study reveals subdiffusive behavior, indicating arrested motion and potential glassy states in granular materials.
Area of Science:
- Physics
- Materials Science
- Chemical Engineering
Background:
- Granular materials exhibit complex dynamics under external stimuli.
- Understanding densification is crucial for predicting material behavior and designing systems.
Purpose of the Study:
- To investigate the densification process in a granular model system.
- To quantify dynamics using mean-square displacement (MSD) and explore temperature and density dependencies.
Main Methods:
- Utilized diffuse wave spectroscopy (DWS) on a vibrating fluidized granular bed.
- Measured MSD to quantify densification and heterogeneous dynamics.
- Employed empirical modeling to extract time constants and caging sizes.
Main Results:
- Demonstrated densification of polystyrene spheres over time with shaking.
- Observed subdiffusive power-law behavior in MSD, indicating motion arrest.
- Found that caging sizes depend on temperature and density, and are smaller than in colloidal systems.
Conclusions:
- The granular system exhibits characteristics of a glassy state under specific excitation conditions.
- Results provide insights into the dynamics and arrest mechanisms in granular materials.
- The study highlights the utility of DWS for characterizing heterogeneous dynamics in granular systems.
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