Simulations of extensional flow in microrheometric devices

Monica Oliveira, Lucy E. Rodd, G.H. McKinley

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Abstract

We present a detailed numerical study of the flow of a Newtonian fluid through microrheometric devices featuring a sudden contraction–expansion. This flow configuration is typically used to generate extensional deformations and high strain rates. The excess pressure drop resulting from the converging and diverging flow is an important dynamic measure to quantify if the device is
intended to be used as a microfluidic extensional rheometer. To explore this idea, we examine the effect of the contraction length, aspect ratio and Reynolds number on the flow kinematics and resulting pressure field. Analysis of the
computed velocity and pressure fields show that, for typical experimental conditions used in microfluidic devices, the steady flow is highly three-dimensional with open spiraling vortical structures in the stagnant corner regions. The numerical simulations of the local kinematics and global pressure drop are in good agreement with experimental results. The device aspect ratio is shown to have a strong impact on the flow and consequently on the excess pressure drop, which is quantified in terms of the dimensionless Couette and Bagley correction factors. We suggest an approach for calculating the Bagley correction which may
be especially appropriate for planar microchannels.
Original languageEnglish
Pages (from-to)809-826
JournalMicrofluidics and Nanofluidics
Volume5
Issue number6
DOIs
Publication statusPublished - Nov 2008

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Keywords

  • microfluidics
  • microrheometry
  • Couette correction
  • Bagley correction
  • contraction-expansion flow
  • extensional flow

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