Laminar mixing of Newtonian and non-Newtonian fluids in SMX static mixer

Abstract

This report is focused on understanding the mixing performance of Newtonian and non-Newtonian fluids in an SMX static mixer through computational fluid dynamics (CFD) study in Simcenter STAR-CCM+. For this, the standard SMX mixer with four mixer elements of radius 26 mm was chosen. The aspect ratio (L/D) was taken as 1. The model constructed was compared using pressure drop ratio values available in literature. First, the design was validated for Newtonian fluid, then for shear-thinning fluid (non-Newtonian). Mixing patterns produced through particle tracking approach revealed how blending improved as the fluid moved downstream and interacted with increasing number of mixer elements. A sensitivity study was undertaken to investigate the effect of particle injection mechanism on the mixing process. Two injection methods, vertical and horizontal, were explored to check the influence of injection position on mixing. The results indicate that for the given configuration irrespective of the injection location, at least four mixing elements are needed to achieve good mixing for both Newtonian and shear-thinning fluids investigated in this study. Statistical reports were used to quantify mixing to understand the mixing behaviour for Newtonian and non-Newtonian fluids with change in Reynolds number. At high Reynolds number, non-Newtonian fluids exhibited better mixing abilities. Further, efforts were taken to optimize the various design parameters to produce the most optimum solution with a single mixer element for Newtonian fluid.