Investigation of the mixing inside the confined impinging jet mixer using the Fokker–Planck mixing model

Abstract

Confined Impinging Jet Mixers (CIJMs) are widely used due to their small-scale-mixing efficiency. This property makes them especially useful for nanoprecipitation. The CIJM process parameters are computationally expensive to predict when using direct-numerical simulation (DNS) and large-eddy simulation (LES). In this work, binary nonreactive mixing of a CIJM is studied using a CFD approach with less computational cost than DNS and LES. The flow field is modelled using Reynolds-averaged Navier–Stokes (RANS) equations and molecular mixing is studied using the Fokker–Planck (FP) molecular-mixing model. The extended quadrature method of moments and generalized quadrature method of moments approaches with β kernel density functions are used to approximate the solution to the evolution of the univariate composition. The results of the flow simulation are compared to experimental and DNS data reported in the literature at various inlet flow rates. Multiple closure models for RANS simulation were investigated in this study. The model that produced the most favorable results was the Launder–Reece–Rodi (LRR) turbulence model due to its ability to handle flow separation and complex vortical structures. The FP mixing model was then employed to resolve the probability density function of a univariate composition to determine the efficacy of mixing at the molecular level for different inlet flow rates. The model used in this study is less computationally expensive than DNS and LES and is shown to be sufficient to accurately capture nanoparticle mixing. Thus, the present work provides a framework for industrial improvement to nanoparticle mixing processes using numerical analysis.