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Dynamical slowdown of polymers in laminar and random flows
A Celani1, A Puliafito, D Vincenzi
1CNRS-INLN, 1361 Route des Lucioles, 06560 Valbonne, France.
Physical Review Letters
|October 10, 2006
Summary
External flow significantly slows polymer relaxation near the coil-stretch transition, especially with conformation-dependent drag. This leads to hysteresis in elongational flows but not random flows, impacting polymer solution modeling.
Area of Science:
- Polymer physics
- Fluid dynamics
- Computational modeling
Background:
- Understanding polymer dynamics in external flows is crucial for applications like drag reduction and biomaterials.
- The coil-stretch transition is a key phenomenon in polymer physics, influencing material properties.
- Previous models often simplified the complex interplay between polymer conformation and flow hydrodynamics.
Purpose of the Study:
- To investigate the influence of external flow on the relaxation dynamics of a single polymer.
- To explore the phenomenon of dynamical slowdown and conformation hysteresis in polymer relaxation.
- To assess the impact of conformation-dependent drag on polymer dynamics.
Main Methods:
- Theoretical analysis of polymer dynamics under external flow.
- Numerical simulations to model polymer behavior.
- Comparison of relaxation times with Zimm relaxation time.
Main Results:
- A pronounced dynamical slowdown occurs near the coil-stretch transition, amplified by conformation-dependent drag.
- Elongational flows exhibit conformation hysteresis, with relaxation times significantly exceeding Zimm relaxation time.
- Random smooth flows do not show hysteresis, but exhibit substantial relaxation slowdown due to diverse configurations.
Conclusions:
- External flow critically alters single polymer relaxation dynamics, particularly near the coil-stretch transition.
- Conformation-dependent drag is a key factor inducing dynamical slowdown and hysteresis.
- Findings have implications for modeling dilute polymer solutions in complex flows, including turbulent environments.
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