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Force and flow transition in plowed granular media
Nick Gravish1, Paul B Umbanhowar, Daniel I Goldman
1School of Physics, Georgia Institute of Technology, Atlanta, Georgia 30332, USA.
Researchers studied granular materials using plate drag, observing a key change in force and flow at the dilatancy point. Above this point, periodic force fluctuations indicate stable shear band formation and destruction.
Area of Science:
- Physics
- Materials Science
- Rheology
Background:
- Granular materials exhibit complex behaviors under stress.
- Understanding the transition from solid-like to fluid-like states is crucial.
Purpose of the Study:
- To investigate the response of granular media to localized forcing.
- To characterize the effect of volume fraction on drag force and flow patterns.
Main Methods:
- Plate drag experiments were conducted on granular media.
- Volume fraction (ϕ) was systematically varied.
- Drag force (F(D)) and velocity fields were measured.
Main Results:
- A critical volume fraction (ϕc) at the onset of dilatancy was identified.
- Below ϕc, drag force showed rapid fluctuations.
- Above ϕc, drag force exhibited periodic fluctuations, increasing with ϕ, linked to shear band dynamics.
Conclusions:
- A bifurcation in granular media response occurs at the onset of dilatancy.
- Stable shear band formation and periodic destruction govern flow above ϕc.
- A friction-based wedge flow model successfully describes the observed dynamics for ϕ > ϕc.
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