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Internal length and time scales in a simple shear granular flow
Hayley H Shen1, Balasubramanian Sankaran
1Department of Civil and Environmental Engineering, Clarkson University, Potsdam, NY 13699-5710, USA. hhshen@clarkson.edu
Physical Review. E, Statistical, Nonlinear, and Soft Matter Physics
|December 17, 2004
Summary
Granular flows show particle groups forming at high shear rates and concentrations, challenging binary collision assumptions. These groups, with extended collision times, necessitate new models for granular material dynamics.
Area of Science:
- Physics
- Engineering
Background:
- Kinetic theory models granular flows using binary collision assumptions.
- Experiments reveal multiple particle collisions dominate at high concentrations or shear rates.
Purpose of the Study:
- Investigate the size and lifetime of multiple collision groups in granular flows.
- Examine how these groups affect flow dynamics and constitutive behavior.
Main Methods:
- Performed computer simulations of 2D granular assemblies with visco-elastic particles.
- Varied shear rate and solid concentration to observe particle interactions.
Main Results:
- Observed formation of distinct particle groups where simultaneous collisions occur.
- Group size and collision duration increase with shear rate and concentration.
- Identified potential formation of force chains spanning the entire assembly.
Conclusions:
- Multiple collisions and group dynamics significantly alter granular flow behavior.
- Current kinetic theory models are insufficient due to additional length and time scales.
- New formulations are required to accurately describe complex granular flows.