velocity is enhanced, especially for Re > 300. For Re > 500 (curves
A and B), the distance corresponding to an established flow
(constant maximum velocity) is 6 angles. Figure 6c shows the
evolution of the maximum outlet velocity (after 8 angles) normalized
to the maximum velocity of the classical Poiseuille profile
for different Reynolds numbers. The shape of the curve is similar
to the one obtained in Figure 5 and illustrates the change of
velocity profiles from a critical Reynolds number of 80. ForReynolds number values ranging from 80 to 300, the generation
of a transversal component of the velocity explains the enhancement
of mixing previously discussed (from 83 to 98.6% for Re
ranging from 80 to 267). For a 3D microchannel, it can be noticed
that the depth effect will slow the local velocity near the walls at
the bottom and top of the channel and damp the recirculations.
The recirculation may be concentrated in the middle of the
channel, decreasing the global mixing effect. However, because
of computational limitations, accurate 3D calculations cannot be
achieved for such geometry and Reynolds numbers.
velocity is enhanced, especially for Re > 300. For Re > 500 (curvesA and B), the distance corresponding to an established flow(constant maximum velocity) is 6 angles. Figure 6c shows theevolution of the maximum outlet velocity (after 8 angles) normalizedto the maximum velocity of the classical Poiseuille profilefor different Reynolds numbers. The shape of the curve is similarto the one obtained in Figure 5 and illustrates the change ofvelocity profiles from a critical Reynolds number of 80. ForReynolds number values ranging from 80 to 300, the generationof a transversal component of the velocity explains the enhancementof mixing previously discussed (from 83 to 98.6% for Reranging from 80 to 267). For a 3D microchannel, it can be noticedthat the depth effect will slow the local velocity near the walls atthe bottom and top of the channel and damp the recirculations.The recirculation may be concentrated in the middle of thechannel, decreasing the global mixing effect. However, becauseof computational limitations, accurate 3D calculations cannot beachieved for such geometry and Reynolds numbers.
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