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Updated: Jun 8, 2026
08:01
The Diffusion of Passive Tracers in Laminar Shear Flow
Published on: May 1, 2018
Passive swimming in low-Reynolds-number flows
1ISAC-CNR and INFN, Sez. Cagliari, Monserrato, Italy.
Physical Review. E, Statistical, Nonlinear, and Soft Matter Physics
|September 28, 2010
Summary
Microscopic swimmers can move by extracting energy from external flows, unlike in still fluids. This study analyzes a trimer
Area of Science:
- Fluid dynamics
- Microswimming
- Biophysics
Background:
- Understanding microscopic swimming is crucial for fields like targeted drug delivery.
- Vesicles in fluid flows exhibit a 'tank-treading' motion, a potential energy extraction mechanism.
- The scallop theorem explains limitations of reciprocal motion in quiescent fluids.
Purpose of the Study:
- To investigate microscopic swimming powered by external flow energy extraction.
- To analyze the migration of a simple trimer in a linear shear flow.
- To explore generalizations for vesicle swimming and energy mechanisms.
Main Methods:
- Theoretical analysis of a discrete trimer model in a linear shear flow.
- Geometric analysis of swimming properties.
- Comparison with vesicle dynamics and the tank-treading regime.
Main Results:
- The trimer extracts energy from the flow for both swimming and 'sailing'.
- Migration velocity scales linearly with stroke amplitude, not quadratically.
- The scallop theorem's non-applicability in external flows is demonstrated.
Conclusions:
- Microscopic swimmers can utilize external flows for propulsion.
- The energy extraction mechanism is analogous to vesicle tank-treading.
- Swimming dynamics in flow differ significantly from those in quiescent fluids.
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