Shear-driven size segregation of granular materials: modeling and experiment
Lindsay B H May1, Laura A Golick, Katherine C Phillips
1Department of Mathematics, North Carolina State University, Raleigh, North Carolina 27695, USA.
Physical Review. E, Statistical, Nonlinear, and Soft Matter Physics
|September 28, 2010
Summary
This study tested a segregation model for granular materials under shear. The model captured mixing and resegregation dynamics but predicted a finite segregation time, unlike the experiment.
Area of Science:
- Physics of granular materials
- Rheology and material science
Background:
- Granular materials exhibit size segregation under shear.
- Predicting segregation time is crucial for understanding granular flow dynamics.
- Existing models are often limited to linear shear profiles.
Purpose of the Study:
- To adapt and evaluate the Gray-Thornton segregation model for exponential shear profiles.
- To compare model predictions with experimental observations of granular segregation.
- To assess the model's ability to capture mixing and resegregation timescales.
Main Methods:
- Experimental setup: annular Couette cell with a moving lower boundary.
- Initial condition: unstable layer of small particles above large particles.
- Data acquisition: measurement of velocity profiles and global dilation.
Main Results:
- The Gray-Thornton model, adapted for exponential shear, successfully captured fast mixing and slower resegregation phases.
- Model predictions showed qualitative agreement with experimental segregation dynamics.
- A discrepancy was observed in the predicted versus experimental resegregation timescale (finite vs. exponential).
Conclusions:
- The adapted Gray-Thornton model provides a valuable framework for understanding segregation in non-linear shear flows.
- Further refinement is needed to accurately predict the timescale of exponential resegregation in granular systems.
- This work contributes to the quantitative understanding of size segregation in granular materials.
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