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Elastic turbulence in a polymer solution flow
1Department of Physics of Complex Systems, Weizmann Institute of Science, Rehovot, Israel.
Nature
|May 16, 2000
Summary
Elastic turbulence, a novel form of fluid instability, occurs in viscoelastic fluids even at low Reynolds numbers. This phenomenon exhibits turbulent characteristics and significantly increases flow resistance, offering new insights into fluid dynamics.
Area of Science:
- Fluid Dynamics
- Rheology
- Polymer Science
Background:
- Turbulence is a complex phenomenon typically associated with high Reynolds numbers in Newtonian fluids.
- Viscoelastic fluids, like polymer solutions, possess unique nonlinear properties that suggest different flow behaviors.
- Understanding turbulence in non-Newtonian fluids is crucial for various industrial applications.
Purpose of the Study:
- To experimentally investigate the flow behavior of viscoelastic polymer solutions.
- To determine if viscoelastic fluids can exhibit turbulence at low Reynolds numbers.
- To characterize the features and consequences of this low-Reynolds-number turbulence.
Main Methods:
- Experimental observation of fluid flow in viscoelastic polymer solutions.
- Varying parameters such as velocity, viscosity, and tank size.
- Analysis of fluid motion across spatial and temporal scales.
- Measurement of flow resistance and elastic stresses.
Main Results:
- Viscoelastic fluid flow becomes irregular and exhibits turbulent characteristics at low Reynolds numbers.
- Flow resistance increased by a factor of approximately twenty compared to expected Newtonian flow.
- Observed turbulence shares key features with high-Reynolds-number turbulence in Newtonian fluids.
- Significant polymer molecule stretching leads to a two-order-of-magnitude increase in elastic stresses.
Conclusions:
- A novel form of turbulence, termed 'elastic turbulence,' is demonstrated in viscoelastic fluids at low Reynolds numbers.
- Elastic turbulence is characterized by broad scale excitation and significantly enhanced flow resistance.
- This finding challenges conventional understanding of turbulence and highlights the distinct behavior of viscoelastic fluids.
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