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Title: Fingering instabilities in viscoelastic liquids

Description: The separation of two plates bridged by a thin layer of a viscoelastic liquid leads to complex instabilities.
The experiment shown was done using a polystyrene Boger fluid characterized by a relaxation time of 3 min.

The larger fingering structure corresponds to a Saffman Taylor instability: a fluid of low viscosity (air) penetrate into a viscous liquid which generates viscous fingering. Elastic stresses in the solution are also induced when the polymeric molecules get stretched enough. They are responsible for the secondary structure which develops at larger strains.

The endplate diameter is 5mm, the initial gap between the endplate is 0.1 mm and the Deborah number (relaxation time/experiment time) is 43.

Credits: Jose Bico, Ryan Welsh, Gareth McKinley

References:

Web Page: http://web.mit.edu/nnf/people/jbico/exp89.mov

Contributed By: Tausif Billah