CFD Performance Analysis of a Stirred Tank Flowmaker

In the present work, the mean flow field in a stirred tank equipped with a commercially available Grundfos AFG.40.230.35 flowmaker is investigated using both steady-state and transient CFD simulation, in order to provide information on the interaction between flow, propeller and wall proximity as well as information on aspects of using numerical tools for this type of fluid machinery. The simulations, carried out with Ansys CFX 10, used a multiple frame of reference (MFR) approach to include a full representation of the flowmaker blade and motor geometry, in order to fully include the effects of the blade shape and variable pitch for both stationary and transient simulations. The influence of grid type, turbulence model and steady vs transient setup on solution quality has been investigated, and the steady state calculations are compared with LDA measurements. The results show that for the steady state calculations, the choice of grid type is decisive in terms of quality of results, and that the transient simulations using the SST turbulence model yields a superior prediction of flow characteristics; however, the computational expenses for transient simulation is around 10 times than steady-state simulation.