Flow structure in a wide microchannel with surface grooves

We present an experimental analysis of pressure-driven flow in a high (62:1) aspect ratio microchannel having a repeated herringbone surface pattern. The velocity field is determined at the groove–channel interface and at the midplane of the channel using microscopic particle image velocimetry. At Reynolds numbers of 0.08, 0.8 and 8, we observe secondary flow patterns consisting of counter-rotating flow cells aligned in the streamwise direction. The strength of this secondary flow is inhibited by fluid inertia when Re=8Re=8. The resulting flow structure can be viewed as splitting one wide channel into multiple smaller channels without the use of solid boundaries.