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Shear-induced segregation of particles by material density
Physical Review. E, Statistical, Nonlinear, and Soft Matter Physics
|September 19, 2015
Summary
Heavier particles segregate to lower shear rates in granular flows, unlike size-segregated flows where reversal occurs. This density-driven segregation persists across all solids fractions, with kinetic theory failing at higher densities.
Area of Science:
- Granular physics
- Multiphase flow dynamics
- Particle segregation phenomena
Background:
- Shear rate gradients drive segregation of particles differing in size, with reversals observed at high solids fractions (>0.50).
- Understanding segregation in granular mixtures with varying densities is crucial for predicting flow behavior.
Purpose of the Study:
- Investigate segregation of particles differing in material density under shear.
- Examine the influence of solids fraction on density-driven segregation.
- Compare segregation behavior to that of size-driven segregation.
Main Methods:
- Computational and theoretical studies of sheared granular mixtures in a vertical chute.
- Systematic variation of solids fraction (〈f〉=0.2 to 0.6).
- Analysis of particle segregation based on density differences.
Main Results:
- In sparse flows (〈f〉=0.2-0.4), denser particles segregate to lower shear rates.
- No segregation reversal observed at high solids fractions for density-driven segregation.
- Denser particles consistently segregate to regions of lower shear rates and granular temperatures.
Conclusions:
- Density-driven segregation differs fundamentally from size-driven segregation, particularly at high solids fractions.
- Existing kinetic theory accurately predicts segregation at low solids fractions but fails at higher ones.
- A proposed mixture theory effectively captures segregation trends by considering independent partitioning of stresses.
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