"CHARACTERIZATION OF DENSE GRANULAR FLOWS USING A CONTINUOUS CHUTE FLOW REHEOMETER" 

Kayli Henry, MSE PhD Candidate 

Advisor: Professor Paul Mort

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ABSTRACT

The ability to predict and manipulate how a particulate material will flow in a process is challenging for industry and researchers alike. This dissertation presents the results of a model-directed, experimental approach using a concentric cylinder rheometer titled along an axis to enable continuous chute flow of granular media. Experiments were performed using draining flows for constant and oscillatory applied shear rates. Multiple flow and stress sensors were used to investigate the interaction of mass holdup, shear rate, specific torque, particle velocity, discharge mass flow rate, and wall pressure. Depending on the flow configuration, linear ranges were observed wherein the specific torque remained steady during draining. This finding enabled systematic testing of flow behavior as a function of dimensionless shear rates. Results suggest changes in the specific torque, wall slip, and outflow variance occur with the transition from the quasi-static to dense-inertial flow regimes. A pump-curve analogy was also identified for the relationship between the outlet mass flow rate and the specific power relationship for the constant shear rate experiments. Oscillatory shear rate experiments show a significant influence of the phase shift between the applied shear rate and the specific torque. Adding an asperity to the rotor revealed rate-dependent patterns is bulk flow and force chain dynamics. Overall, the study offers valuable insights into the effects of shear rate and boundary conditions on dense granular flows. The effects of particle characteristics (e.g., size and shape distributions, friction, cohesivity) and material properties (e.g., density, modulus) remain topics for future work.