Experiment and depth-averaged analysis of water flow in contraction-expansion microchannels

The entry flow through a sudden contraction is a classical multidimensional problem that has been studied for decades. It becomes even more complicated in planar geometries that are typical in the microfluidics community because of the standard soft lithography technique. A three-dimensional simulation of such a flow, though proving accurate, is inevitably time-consuming and computationally expensive. Considering the fact that the planar microfluidic channels often have a small width/depth aspect ratio, we present in this work a generalized depth-averaged model suitable for studying the flow behavior in microfluidic devices with shallow-channel geometries. We demonstrate this idea by comparing the prediction of a depth-averaged analysis with both the three-dimensional simulation and the experimental observation for water flow through planar contraction-expansion microchannels of varying depths under varying flow rates.