Related Experiment Videos
Transport on intermediate time scales in flows with cat's eye patterns.
Patrick Pöschke1, Igor M Sokolov1, Michael A Zaks1
1Institute of Physics, Humboldt University of Berlin, Newtonstr. 15, D-12489 Berlin, Germany.
Physical Review. E
|January 20, 2018
Summary
This study explores tracer movement in complex fluid flows, revealing transport behavior from subdiffusive to superballistic. Numerical simulations and Lévy walk theory highlight emergent aging dynamics not predicted by standard models.
Area of Science:
- Fluid Dynamics
- Transport Phenomena
- Statistical Mechanics
Background:
- Periodic flows with "cat's eye" circulation regions and meandering jets exhibit complex tracer transport.
- Adding thermal noise (large Péclet numbers) introduces multiple time scales and diverse transport behaviors.
Purpose of the Study:
- Investigate tracer advection-diffusion in a parameterized family of plane periodic flows.
- Characterize the transition from eddy lattices to modulated shear flows.
- Analyze the impact of flow parameters, initial conditions, and aging on tracer motion.
Main Methods:
- Numerical simulations of mean-squared displacement for various initial conditions and aging times.
- Comparison of simulation results with Lévy walk theory for ballistic transport regimes.
Main Results:
- Tracer motion spans subdiffusive to superballistic regimes depending on flow parameters, initial position, and aging time.
- A Lévy walk model reasonably describes intermediate-time ballistic transport for some conditions.
- Internal circulation dynamics lead to non-monotonic aging characteristics not captured by the Lévy walk model.
Conclusions:
- Complex fluid flows exhibit rich tracer transport dynamics with distinct intermediate time scales.
- Lévy walk theory provides partial insight but fails to capture all emergent aging phenomena.
- The interplay between ballistic motion and trapped circulation dynamics is crucial for understanding aging in these systems.