Passive Mixing

Passive Mixing and Concentration Tracking Using Scalars

The mixing of multiple streams of fluids in micro channels/chambers is of great importance in bio-analytical systems. Typically these processes need to occur within short mixing lengths and time scales. Passive micro-mixers make use of the geometry of the micro-channel to induce mixing. Shown here is a design variation where the liquid plus reagent side uses a passive scalar to show the mixing concentration. In this case, the two fluids had nearly identical viscosities but FLOW-3D is capable of modeling different viscosities and densities mixing as well.

Passive mixing scematic biotech
Schematic showing just how small a desired mixing length can be. The pure liquid will enter the top and the mixture will enter the bottom; flow is from left to right. Ideally, the two streams would be fully mixed by the end of the 2000micron chamber.

CFD Simulation of Passive Mixing

Demonstration of a passive micro channel mixing process. The colors represent the concentration of the two different fluids (blue =  Pure liquid, red = Liquid + Reagent).