Influence of impeller type on the flow structure in a stirred reactor

Large eddy simulations (LES) of a stirred reactor with a liquid volume of 0 .64 m(3) were performed. The tank was stirred by either two standard Rushto n impellers or two Scaba 6SRGT impellers. The LES can provide details of th e flow field that cannot be obtained with so-called Reynolds-averaged equat ions and the corresponding models. The unsteady spatially filtered incompre ssible Navier-Stokes equations were solved together with a transport equati on for the concentration of an inert additive using a multigrid finite diff erence code with a staggered grid. The unresolved turbulent scales were mod eled using a scale similarity model. The aim of this investigation has been to study the influence of impeller type on the flow structure and scalar t ransport. The results show that, compared at equal power input, the center plane velocities and the volume flow in the impeller stream do not differ m uch for the impeller types. Also, for the 6SRGT the periodic fluctuations a ssociated with the blade passing is less pronounced.