Time dependent fluid dynamics and Lagrangian tracking to model 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 flow field is calculated with a computationally effcient procedure using a RANS solver with k–epsilon turbulence modeling and the $ow 8eld is assessed precisely against experimental data. Then, fluid parcels are tracked in the calculated flow field. Analyzing the trajectory of fluid parcels, the segregated regions within the flow are identified 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 fluid dynamics generated by the interactions of radial-discharge jet, ring vortices, and upper counter rotating vortex.