Drag enhancement and drag reduction in viscoelastic flow Journal Article

Author(s): Varshney, Atul; Steinberg, Victor
Article Title: Drag enhancement and drag reduction in viscoelastic flow
Affiliation IST Austria
Abstract: Creeping flow of polymeric fluid without inertia exhibits elastic instabilities and elastic turbulence accompanied by drag enhancement due to elastic stress produced by flow-stretched polymers. However, in inertia-dominated flow at high Re and low fluid elasticity El, a reduction in turbulent frictional drag is caused by an intricate competition between inertial and elastic stresses. Here we explore the effect of inertia on the stability of viscoelastic flow in a broad range of control parameters El and (Re,Wi). We present the stability diagram of observed flow regimes in Wi-Re coordinates and find that the instabilities' onsets show an unexpectedly nonmonotonic dependence on El. Further, three distinct regions in the diagram are identified based on El. Strikingly, for high-elasticity fluids we discover a complete relaminarization of flow at Reynolds number in the range of 1 to 10, different from a well-known turbulent drag reduction. These counterintuitive effects may be explained by a finite polymer extensibility and a suppression of vorticity at high Wi. Our results call for further theoretical and numerical development to uncover the role of inertial effect on elastic turbulence in a viscoelastic flow.
Journal Title: Physical Review Fluids
Volume: 3
Issue 10
ISSN: 2469990X
Publisher: American Physical Society  
Date Published: 2018-10-15
Start Page: article number: 103302
DOI: 10.1103/PhysRevFluids.3.103302
Notes: A.V. acknowledges support from the European Union's Horizon 2020 research and innovation program under the Marie Skłodowska-Curie Grant Agreement No. 754411. This work was partially supported by Israel Science Foundation (Grant No. 882/15) and Binational U.S.-Israel Foundation (Grant No. 2016145).
Open access: no