Biomedical Engineering Reference
In-Depth Information
FIGURE 6.22
Concentration distribution in an SHM: (a) at the inlet; (b) after the first cycle; (c) after the second cycle; (d) after
the third cycle; and (e) after the fourth cycle.
(Redrawn after experimental results of Stroock et al. [25] .)
field. Next, particles of mixing fluids are tracked according to the predetermined velocity field (see
Chapter 2). The particles are “colored” according to the type of fluids. The final distribution of colored
particles allows the evaluation of mixing efficiency in the micromixer. Optimization studies by Lynn
and Dandy [32] lead to the following conclusions:
Chaotic advection in SHM leads to more efficient mixing than the helical flow in SGM.
The optimized width fraction of the herringbone structure is approximately p ¼W 1 / 2/3.
The optimized angle of grooves and ridges is 45 .
The magnitude of the secondary transversal flow is weakly dependent on the channel aspect
ratio H / W .
The magnitude of helical flow is strongly dependent on the groove depth (ridge height) ratio h / H .
The higher the ratio h / H , the more efficient is the mixing process.
It is apparent that mixing is improved if the transversal secondary flow is strong relative to the axial flow.
A strong secondary flow also increases the chance of angular displacement leading to a shorter mixing
channel. A large groove would allowmore mass transport in transversal direction, while the axial flow is
affected by the flow within the groove. Lynn and Dandy [32] focused on the numerical optimization on
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