Paper Number
IN9 

Session
Flow-induced Instabilities in Non-Newtonian Fluids

Title
Inertio-elastic instabilities in free shear and wall-bounded flows

Presentation Date and Time
October 12, 2022 (Wednesday) 10:30

Track / Room
Track 5 / Sheraton 2

Authors (Click on name to view author profile)

  1. Yamanidouzisorkhabi, Sami (MIT, Mechanical Engineering)
  2. Raj, Yashasvi (MIT, Mechanical Engineering)
  3. Zaki, Tamer A. (Johns Hopkins University, Mechanical Engineering)
  4. McKinley, Gareth H. (Massachusetts Institute of Technology, Mechanical Engineering)
  5. Bischofberger, Irmgard (MIT)

Author and Affiliation Lines (in printed abstract book)
Sami Yamanidouzisorkhabi1, Yashasvi Raj1, Tamer A. Zaki2, Gareth H. McKinley1 and Irmgard Bischofberger1
1Mechanical Engineering, MIT, Cambridge, MA 02139; 2Mechanical Engineering, Johns Hopkins University, Baltimore, MD 21218

Speaker / Presenter 
Yamanidouzisorkhabi, Sami

Keywords
flow-induced instabilities; polymer solutions

Text of Abstract
The addition of small amounts of long-chain macromolecules to a Newtonian solvent can lead to significant frictional drag reduction in high-speed shear flows. The interaction of viscoelasticity and inertia in a dilute polymer solution results in the emergence of unique inertio-elastic instabilities. The nonlinear evolution of these instabilities engenders a state of turbulence with significantly different spatiotemporal features compared to Newtonian turbulence, commonly termed elasto-inertial turbulence (EIT). We explore these inertio-elastic instabilities as pathways to EIT in free shear and wall-bounded flows. Free shear flows are explored by studying the dynamics of submerged round and planar jets of dilute aqueous polymer solutions injected into a quiescent tank of water. We show how fluid elasticity has a dichotomous effect on jet stability, depending on its magnitude, creating two distinct regimes in which elastic effects can either destabilize or stabilize the laminar jet. For small levels of elasticity, an inertio-elastic shear layer instability emerges at the edge of the jet. The growth of this instability destabilizes the flow, advancing the transition to turbulence to lower Reynolds numbers and closer to the nozzle. Increasing the fluid elasticity couples this surface shear layer mechanism with the bulk dynamics of the fluid column. In this regime, elastic tensile stresses generated in the shear layer act as an “elastic membrane” that stabilizes the flow, retarding the transition to turbulence to higher levels of inertia and greater distances from the nozzle. To explore the pathways to EIT in polymer boundary layer injection systems, we introduce bounding channel walls using a recirculating channel flow system.