Entrance Length of Low Reynolds Number Flow in Microchannel

The entrance lengths in rectangular microchannels with planar reservoirs, geometries typically produced with microfabrication techniques, have been investigated in the low Reynolds number range, 1 < ReD < 100. Two microchannels having the complementary aspect ratios (H/W) of 2.75 and 0.37 are fabricated and tested. The hydraulic diameters of two microchannels are ~370 μm and ~56.4 μm. μPIV is used to measure the velocity profiles and the entrance lengths are found from the curve fitted centerline velocity growth. The entrance lengths in the channels with planar upstream reservoirs are found to be significantly different from those with infinite upstream reservoirs.