Transverse flow at the flight surface in flighted rotary drum

• Kinetic angle of repose is determined by extending the model of Schofield and Glikin.
• A thin cascading layer is assumed to exist at the flight surface.
• The Eulerian approach is followed to determine the transverse velocity profiles in the flight.
• Effect of flight length ratio and dynamic angle of repose is presented.

Rotary drums, installed with longitudinal flights are often used to dry/cool granular materials in large quantities. The rate of solids falling down from the flights determines the amount of material responsible for the contact between the solids and hot air stream, which primarily depends on the angle of repose at the flight surface. In this study, the model of Schofield and Glikin has been extended by considering a flowing layer at the flight surface and inertial force acting in the cascading layer due to the rotation of the drum. The corresponding velocity profile for the layer has been predicted by following the Eulerian approach by treating the granular flow as a continuum similar to the transverse flow in rotating drums without flights. To validate the model, experiments were carried out at a laboratory drum of 0.5 m in diameter using quartz sand, glass beads and steel balls of different particle sizes at various drum rotations. The measured data is compared with the model predictions under different experimental conditions. The experimental data showed good agreement with the model predictions.

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