Effects of planar inlet plenums on the hydrodynamically developing flows in rectangular microchannels of complementary aspect ratios

Abstract

The effects of planar inlet plenum geometry on the developing flow fields in two rectangular microchannels of reciprocal aspect ratios (H/W~2.75 and~0.40) were investigated for Re D = 1-100 using micro particle image velocimetry (lPIV). These two microchannels were made by a precision sawing and silicon microfabrication techniques. Both the velocity profiles and centerline velocity developments were clearly resolved and extracted along the axial distance from lPIV results. The entrance lengths were found from the centerline velocities using a decaying exponential fitting function where the centerline velocity reaches 99% of the fully developed centerline velocity. The proposed fitting function showed excellent agreement with the experimental results. The planar plenum was shown to cause an upstream predevelopment resulting in the significant reductions in the entrance lengths. Two entrance length correlations were proposed in the forms of Atkinson et al. 's (AIChE J 15:548-553, 1969) and Chen's (J Fluids Eng 95:153-158, 1973) correlations. The proposed entrance length correlations showed that acquired constant portion and slope of the entrance lengths showed 23-27 and 70-81% reductions for H/W = 2.75 while the entrance length correlation for H/W = 0.40 showed 69-73% increase and 41-63% decrease in the constant portion and slope, respectively.

Measurement and modeling of pulsatile flow in microchannel

“…Using this expression, the maximum entrance length for the present set of experiments is about 2.9 mm. As per the correlation provided by Lee et al (2008), the maximum entrance length comes out to be 2.4 mm. Therefore, for most of the cases the development length is less than 15% of the total length (=20 mm), which is within the acceptable limits.…”

Viscoelastic flow development in planar microchannels

“…Lee et al 2008;Ahmad and Hassan 2010). Lee et al (2008) explained the initial skewed inlet flow as being due to a slightly asymmetric flow path from the reservoir to the channel entrance, especially for downstream channels with small dimensions. In our work, there is no obvious skewness of the inlet flow profiles (i.e.…”

“…For the flow of Newtonian fluids in two microchannels with different aspect ratios α = h/w (where h is the channel depth and w is the channel width) and over a range of Reynolds numbers 1 ≤ Re ≤ 100, Lee et al (2008) reported the entry length has a much weaker dependence on Reynolds number compared with the correlations obtained in conventional macroscopic channels. In general, the entry length in microchannels was significantly smaller than expected, which was attributed to the uniform height of the channels upstream and downstream of the entrance region and hence the flow being "predeveloped" in the neutral direction (i.e.…”

Optofluidics incorporating actively controlled micro- and nano-particles

“…10 They are used as the labels for revealing the presence and tracing the movement of such particles. Light scattering is another method of detecting and analyzing particles.…”

“…Despite these reviews, we have found that the subject matter of our review has not been specifically covered in literature. The review by Lee et al, 10 for example, focuses primarily on surface enhance Raman spectroscopy (SERS) and plasmonic applications of colloidal optofluidics. In addition, the reviews by Tsutsui and Ho 11 and Lenshof and Laurell 12 describe particle and cell separations in microfluidic systems but do not concentrate on optofluidic devices and systems.…”