Paper Number
GR2 

Session
Gallery of Rheology Contest

Title
The ins and outs of elastic instabilities in cross-slot flows: A 3D experimental view

Presentation Date and Time
October 17, 2018 (Wednesday) 6:30

Track / Room
Gallery of Rheology / Woodway Foyer

Authors (Click on name to view author profile)

1. Qin, Boyang (Princeton University, Mechanical and Aerospace Engineering)
2. Ran, Ranjiangshang (University of Pennsylvania, Mechanical Engineering and Applied Mechanics)
3. Salipante, Paul F. (National Institute of Standards and Technology, Polymers and Complex Fluids Group)
4. Hudson, Steven (NIST, Polymers and Complex Fluids Group)
5. Arratia, Paulo E. (University of Pennsylvania, Mechanical Engineering & Applied Mechanics)

Author and Affiliation Lines (in printed abstract book)
Boyang Qin¹, Ranjiangshang Ran², Paul F. Salipante³, Steven Hudson³, and Paulo E. Arratia^2
1Mechanical and Aerospace Engineering, Princeton University, Princeton, NJ 08544; ²Mechanical Engineering & Applied Mechanics, University of Pennsylvania, Philadelphia, PA; ³Polymers and Complex Fluids Group, National Institute of Standards and Technology, Gaithersburg, MD 20910

Speaker / Presenter 
Arratia, Paulo E.

Text of Abstract
It is well known that polymer molecules can be strongly stretched (and compressed) by the hyperbolic point of a cross-slot flow. Molecules exert forces back on the fluid and, at a critical Weissenberg number (Wi), this lead to a symmetry breaking flow instability in the plane of extension. As the Wi is increased even further, this symmetry breaking instability becomes time-dependent. Here, we use a three-dimensional (3D) holographic particle tracking technique to visualize the flow and find a new symmetry-breaking instability to the extension plane, marked by bi-stable flow switching and "buckling" of the separatrix between the impinging streams. Our results shows that in the polymer game of chicken, escape routes are highly three-dimensional.