Continuum modeling of multi-regime particle flows in high-shear mixing

Abstract

This article compares and evaluates different approaches for continuum modeling in high shear mixers covering the full range of the solid volume fraction. High shear mixing is considered as the first stage in industrial high shear granulation processes. The study is focused on and compared with experimental data for a MiPro mixer. Different granular flow regimes are located in different regions of the system and suitable models are applied for each region. Accordingly, the dilute regions are modeled with the standard kinetic theory of granular flow (KTGF) model. The dense regions are modeled using a framework developed by Jop et al. [1] which treats dense flows with pseudo-plastic rheology. The transitional region from dilute to dense is either modeled with KTGF or by using modifications to the transport coefficients that describe the solid phase stresses as proposed by Bocquet et al. [2] (the viscosity divergence model). The results using the latter model show significant improvement compared to similar studies in the past. A very good agreement between simulation and experiments is achieved. It should be noted that the proposed modeling frameworks are formulated for the full range of volume fractions and can be applied to various particulate flows. To sum up, this research provides a better description of multi-regime granular flows, particularly the transitional behavior in the intermediate range of volume fractions.