Nonlinear elastic instability in channel flows at low Reynolds numbers

It is presently believed that flows of viscoelastic polymer solutions in geometries such as a straight pipe or channel are linearly stable. Here we present experimental evidence that such flows can be nonlinearly unstable and can exhibit a subcritical bifurcation. Velocimetry measurements are perfor...

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Bibliographic Details
Published in:Physical review letters 2013-04, Vol.110 (17), p.174502-174502, Article 174502
Main Authors: Pan, L, Morozov, A, Wagner, C, Arratia, P E
Format: Article
Language:English
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Summary:It is presently believed that flows of viscoelastic polymer solutions in geometries such as a straight pipe or channel are linearly stable. Here we present experimental evidence that such flows can be nonlinearly unstable and can exhibit a subcritical bifurcation. Velocimetry measurements are performed in a long, straight microchannel; flow disturbances are introduced at the entrance of the channel system by placing a variable number of obstacles. Above a critical flow rate and a critical size of the perturbation, a sudden onset of large velocity fluctuations indicates the presence of a nonlinear subcritical instability. Together with the previous observations of hydrodynamic instabilities in curved geometries, our results suggest that any flow of polymer solutions becomes unstable at sufficiently high flow rates.
ISSN:0031-9007
1079-7114
DOI:10.1103/physrevlett.110.174502