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Elastic turbulence in a curvilinear channel flow
Yonggun Jun1, Victor Steinberg
1Department of Physics of Complex Systems, Weizmann Institute of Science, Rehovot, Israel.
Physical Review. E, Statistical, Nonlinear, and Soft Matter Physics
|December 21, 2011
Summary
Elastic turbulence in polymer solutions shows a boundary layer where elastic stresses concentrate. These stresses may eject into the bulk flow, challenging current elastic turbulence theories.
Area of Science:
- Fluid Dynamics
- Polymer Physics
- Rheology
Background:
- Elastic turbulence is a flow regime in viscoelastic fluids driven by elastic instabilities.
- Understanding elastic turbulence is crucial for applications involving polymer solutions, such as drag reduction and microfluidics.
Purpose of the Study:
- To quantitatively investigate elastic turbulence in a curvilinear channel flow of a dilute polymer solution.
- To analyze the distribution of elastic stresses and their impact on velocity profiles.
- To compare experimental findings with existing theories of elastic turbulence.
Main Methods:
- Detailed quantitative studies of average and root-mean-square (rms) velocity and velocity gradients.
- Analysis of velocity and velocity gradient correlation functions.
- Experiments conducted in a high viscosity water-sugar solvent with high molecular weight polyacrylamide.
Main Results:
- A boundary layer emerges due to non-uniform elastic stress distribution, with a width independent of the Weissenberg number (Wi).
- Evidence suggests ejection of concentrated elastic stresses from the boundary layer into the bulk flow.
- Experimental results contradict theoretical predictions regarding the saturation of normalized rms velocity gradients in the bulk flow.
Conclusions:
- The study highlights the significant role of boundary layers in elastic turbulence within bounded geometries.
- Experimental findings necessitate further theoretical development for elastic turbulence in confined flows.
- Discrepancies between theory and experiment regarding velocity gradients call for revised theoretical models.
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