Laminar Static Mixer Analysis

Technical Challenge

Laminar static mixers work by periodically dividing and recombining fluids until they are well mixed.  The performance of these mixers is impossible to analyze with a pure CFD (computational fluid dynamics) approach due to the limited molecular diffusion between the mixed fluids.  Veryst Engineering collaborated with Nordson EFD to develop computational models of their laminar static mixers and find ways to improve and optimize their performance.
 

Veryst Solution

We developed a new modeling tool for analyzing laminar static mixers that involves CFD analysis, particle tracing, and a novel mixing analysis algorithm.  We first perform a CFD analysis of the overall mixer performance (using COMSOL Multiphysics), and predict the overall flow pattern and pressure drop. 

We then apply a grid of over 200,000 streamline or massless particles to follow the path of fluid particles with very little numerical diffusion.  Finally, we generate cross-sectional mixing images at mixer cross-sections to identify unmixed fluid regions, and compare the images to experimental tests conducted by Nordson EFD.

Laminar Static Mixers Catalogue
Figure 1. Laminar static mixers (image courtesy of Nordson EFD)

 

Figures 2 and 3 show the velocity profile and streamlines through a section of one of Nordson’s static mixers.

Velocity Profile
Figure 2. Velocity profile at different sections along static mixer

 

Streamline Fig2b
Figure 3. Streamline plot showing fluid mixing at first four mixing elements

 

Figure 4 shows a comparison between experimental images from a mixer and the corresponding numerical predictions at three different cross-sections all along the first half of the mixer.  The algorithm successfully identified the unmixed fluid regions throughout the mixer.

Mixing cfd experimental
Figure 4. Comparison between experimental results and numerical mixing predictions

 

For more details see the Modeling of Laminar Flow Static Mixers article published in COMSOL News 2012.

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