Effects of turbulence modeling on the prediction of flow characteristics of mixing non-Newtonian fluids in a stirred vessel

Abstract

Mixing characteristics of the non-Newtonian fluid in a stirred vessel with a side-entry novel propeller was investigated by using computational fluid dynamics (CFD). The SST model (SST), standard k-ω (SKO), Reynold stress model (RSM), standard k-ε (SKE), Realizable k-ε (KER), RNG k-ε (RNG) were evaluated for nine generalized Reynolds numbers operating at different flow conditions. In order to determine the estimated trait generalized Reynolds number at the end of the laminar regime, both the laminar and turbulent model simulations were conducted. Those results were validated with the published literature experimental results and different simulated results. By comparing the simulated and experimental literature results, the SST and RSM models are found to be more accurate than the other four turbulence models in predicting the torque. The power consumption and power numbers curves calculated from the SST and RSM models are highly consistent with the experimental results. To verify the effect of the applied turbulence models on predictive accuracy, both the velocity field, streamlines distributions, and the velocity profiles are evaluated. The RSM model was found to be more realizable for capturing mixing behavior in lower concentration solutions and with lower rotation speeds. However, this model has some drawbacks for modeling stirred vessels, such as a large number of modeled revolutions and mesh statistical required to obtain good quantities. In contrasts with the RSM model, the SST model is more reliable to predict velocity profiles and flow patterns in higher concentration solutions, especially in the near wall region.