Mixing process shear flow

In laminar flow, a similar mixing process occurs when the liquid is sheared between two rotating cylinders. During each revolution, the thickness of the fluid element is reduced, and molecular diffusion takes over when the elements are sufficiently thin. This type of mixing is shown schematically in Figure 7.3 in which the tracer is pictured as being introduced perpendicular to the direction of motion. 

A biological application, bacteria capture by mixing of blood/bacteria samples with magnetic beads, was carried out in the L-shaped micro mixer [49], A high capture efficiency of 99% was obtained at a short time of 0.15 s. The blood cells and bacteria remained intact after the mixing process, evidencing the low shear strain field of the flow. 

First and foremost, the laminar mixing flow created in the reactive processing equipment, must reduce the striation thickness to a level where the diffusion characteristic time, tD = r2/ )AB, is small compared to the reaction characteristic time. Since the molecular diffusivities of low molecular weight components in polymeric melts (see Section 8.3) are very small and of the order of 10 6 cm2/s, the striation thickness must be reduced to the micron level in order to get a characteristic time t of the order of 1 s. Shear flow can accomplish this in reasonable mixing times because the striation thickness is inversely proportional to the total shear (see Section 7.3)... 

Fig. 11.37 Suppression of shear flow-induced coalescence by incorporating a very low concentration of SIS triblock compatibilizer into the equiviscous Blend 2. [Reprinted by permission from the Proceedings of the Tenth Semi-annual Meeting of the Polymer Mixing Study, Polymer Processing Institute, Hoboken, NJ (1995).]...

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