paper

Drag enhancement and drag reduction in viscoelastic flow

arXiv:1809.03778 · doi:10.1103/PhysRevFluids.3.103302

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 $\mbox{Re}$ and low fluid elasticity , 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 and $(\mbox{Re}, \mbox{Wi})$. We present the stability diagram of observed flow regimes in $\mbox{Wi}-\mbox{Re}$ coordinates and find that instabilities' onsets show unexpectedly non-monotonic dependence on . Further, three distinct regions in the diagram are identified based on . Strikingly, for high elasticity fluids we discover a complete relaminarization of flow at Reynolds number of the order of unity, 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 $\mbox{Wi}$. Our results call for further theoretical and numerical development to uncover the role of inertial effect on elastic turbulence in a viscoelastic flow.

arXiv comment8 pages, 6 figures

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