Elastic flow instabilities in microfluidic serpentine channels
We discuss the onset of a purely elastic flow instability in serpentine channels, using a combined experimental, numerical and theoretical investigation. Good qualitative agreement is obtained between experiments, using dilute solutions of flexible polymers in microfluidic devices, and three-dimensional numerical simulations using the upper-convected Maxwell model  The results are confirmed by a simple theoretical analysis, based on the dimensionless criterion proposed by Pakdel & McKinley (PRL, 1996). We then determine the influence of fluid shear thinning on the onset of such purely-elastic flow instabilities and observe that shear thinning has a stabilizing effect on the microfluidic flow . Three-dimensional numerical simulations performed using the White–Metzner model predict similar trends, which are not captured by a
simple scaling analysis using the Pakdel–McKinley criterion.
The good understanding of the onset of elastic instabilities can also be used to determine relaxation times of unknown solutions and we describe a microfluidic rheometer using a serpentine flow channel . In addition, we investigate the structure and magnitude of secondary flows, present in flows of visco-elastic fluids in curved geometries [3,5].
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Nanofluid (2019) 23: 33