Power Consumption And Granular Flow In A Vibro-Fluidized Stirred Granular Bed

This work examines the behavior of a deep granular bed subject to simultaneous vertical vibration and stirring. The power necessary to stir a 5.6 cm diameter and 20 cm deep granular bed of 150 micron glass beads using a 4-blade vane impeller was measured over a wide range of forcing conditions. Impeller rotation rates from 0 - 1000 rpms and vibration accelerations in the range 0 $\le \quad \Gamma =\omega ^{2}$a/g $\le $ 4.0 were explored. Both the power required for stirring and vibration were recorded. Sharp changes in vane power draw indicate flow transitions from dense granular flow to vibro-fluidized flow at a critical acceleration ($\Gamma _{c})$. The total power profile (vane plus vibration power) demonstrates a minimum just above the critical acceleration. Progressive increases or decreases in both vane speed and $\Gamma $ independently show hysteresis as the flow bifurcates between two primary states of dense granular flow and loose-packed, vibrofluidized behavior. Finally, preliminary results of direct density measurements using a localized capacity probe will be discussed. These observations are compared to those found in fluidized systems and flows generated in high-shear granulators.