Static Mixers – Turbulent Mixing

Static or motionless mixers are fins, obstructions, or channels mounted in pipes, designed to promote mixing. The flow is either divided, rotated, channeled, or diverted through each stage of the mixer. Static mixers can also be used to generate turbulence to enhance mixing.

The power input to the mixing process is a result of pressure loss through the mixer. Static mixers can be used for blending after additive injection, blending for uniform temperature or concentration profiles, or multi-phase dispersion. Some types of mixers are better for turbulent flow or laminar flow, while others work well over a wide range of fluid properties.

HEV Static Mixer

A circular or square cross-section of pipe with sets of tabs mounted on the walls. Flow around the tabs is unsteady, with counter-rotating longitudinal vortices and hairpin vortices. Courtesy of Chemineer Inc.

Large eddy simulation (LES) predicts an unsteady vortex system including transient hairpin vortices, as also seen in experiments. Interaction between the vortices causes material exchange between tabs, and between the center and tabs.