A positron emission particle tracking investigation of the scaling law governing free surface flows in tumbling mills

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• 作者：Indresan Govender ; Max C. Richter ; Aubrey N. Mainza and David N. De Klerk
• 刊名：AIChE Journal
• 出版年：2017
• 出版时间：March 2017
• 年：2017
• 卷：63
• 期：3
• 页码：903-913
• 全文大小：951K
• ISSN：1547-5905

文摘

Positron Emission Particle Tracking (PEPT) measurements are used to track the flow of d=5 mm glass beads within a rotating drum fitted with (and without) lifter bars and operated in the cascading and cataracting Froude regimes. After converting the Lagrangian trajectories of a representative radio-labeled glass bead (the tracer) into Eulerian fields under the ergodic assumption, the bed shape and kinematics are extracted for steady, fully developed flow conditions. Notwithstanding the azimuthal wall effects introduced by the lifter bars, we show a linear scaling 〈v〉∝h of the local flowing layer thickness (h) with local depth-averaged velocity 〈v〉 and a constant average shear 〈γ̇〉∼0.6gd for direct measurements spanning the entire flowing layer (not just the central region), and high Froude regimes (cascading and cataracting) not previously investigated by scaling analysis in the literature.