Paper Number
IN29 

Session
Flow Induced Instabilities and Non-Newtonian Fluids

Title
Upstream vortex and elastic wave in the viscoelastic flow around a confined cylinder

Presentation Date and Time
October 23, 2019 (Wednesday) 9:50

Track / Room
Track 4 / Room 305B

Authors (Click on name to view author profile)

  1. Qin, Boyang (Princeton U, Dept. of Mechanical & Aerospace Engineering)
  2. Salipante, Paul F. (NIST, Polymers & Complex Fluids)
  3. Hudson, Steven (NIST)
  4. Arratia, Paulo E. (University of Pennsylvania, Mechanical Engineering and Applied Mechanics)

Author and Affiliation Lines (in printed abstract book)
Boyang Qin1, Paul F. Salipante2, Steven Hudson2, and Paulo E. Arratia3
1Dept. of Mechanical & Aerospace Engineering, Princeton U, Princeton, NJ 08540; 2Polymers & Complex Fluids, NIST, Gaithersburg, MD 20899; 3Mechanical Engineering and Applied Mechanics, University of Pennsylvania, Philadelphia, PA 19104

Speaker / Presenter 
Hudson, Steven

Text of Abstract
The flow of a viscoelastic fluid past a cylinder is a classic benchmark problem that is not completely understood. Using novel holographic particle velocimetry to measure 3D flow fields, we report two main discoveries of the elastic instability upstream of a single cylinder in confined microchannel flow. After the onset of corner vortices upstream of the cylinder, we find that the vortex becomes unsteady and switches between two distinct flow states, leading to symmetry breaking perpendicular to the cylinder axis that is highly three-dimensional in nature. Second, we show that the disturbance of the elastic instability propagates far upstream via an elastic wave and is weakly correlated with that in the cylinder wake. The wave speed and the extent of the instability increase with Weissenberg number, indicating an absolute instability in viscoelastic fluids.