Time-dependent flow structures and Lagrangian mixing in Rushton-impeller baffled-tank reactor

The object of this work is to investigate the role of large-scale convective structures in promoting mixing in a stirred tank. We focus on a standard geometry ($at bottom, four-ba*e reactor stirred by a six-blade Rusthon impeller) and we use an Eulerian–Lagrangian approach to investigate numerically the dispersion of $uid particles. The three-dimensional, time-dependent, fully developed $ow 8eld is calculated with a computationally e9cient procedure using a RANS solver with k–� turbulence modeling and the $ow 8eld is assessed precisely against experimental data. Then, $uid parcels are tracked in the calculated $ow 8eld. Analyzing the trajectory of $uid parcels, the segregated regions within the $ow are identi8ed and mixing indicators are calculated (mixing time, circulation length and sojour time distribution). A physical explanation is thus proposed to establish a link between large-scale mixing and complex $uid dynamics generated by the interactions of radial-discharge jet, ring vortices, and upper counter rotating vortex. ? 2003 Elsevier Science Ltd. All rights reserved.

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