Nonlinear Elastic Instability in Channel Flows at Low Reynolds Numbers

L. Pan, A. Morozov, C. Wagner, and P. E. Arratia

Phys. Rev. Lett. 110, 174502 – Published 23 April 2013

Abstract

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.

Received 20 April 2012

DOI:https://doi.org/10.1103/PhysRevLett.110.174502

Authors & Affiliations

L. Pan¹, A. Morozov², C. Wagner³, and P. E. Arratia¹

¹Department of Mechanical Engineering and Applied Mechanics, University of Pennsylvania, Philadelphia 19141, USA
²SUPA, School of Physics and Astronomy, University of Edinburgh, Mayfield Road, Edinburgh EH9 3JZ, United Kingdom
³Experimental Physics, Saarland University, 66123 Saarbrucken, Germany