Dynamics of nearly spherical vesicles in an external flow
V V Lebedev1, K S Turitsyn, S S Vergeles
1Landau Institute for Theoretical Physics, Moscow, Kosygina 2, 119334, Russia.
Physical Review Letters
|February 1, 2008
Summary
Vesicle dynamics in flow exhibit tank-treading, tumbling, and trembling behaviors. Transitions between these states are governed by flow parameters and bifurcations, with dynamics slowing down near transition points.
Area of Science:
- Fluid dynamics
- Biophysics
- Soft matter physics
Background:
- Vesicles display complex behaviors like tank-treading, tumbling, and trembling in external flows.
- Understanding these dynamics is crucial for various applications, including drug delivery and microfluidics.
Purpose of the Study:
- To derive a dynamical equation for nearly spherical vesicles in 2D external flow.
- To analyze the transitions between different vesicle dynamic states (tank-treading, tumbling, trembling).
- To investigate the slowdown of vesicle dynamics near transition points.
Main Methods:
- Derivation of a dynamical equation for vesicle behavior.
- Analysis of vesicle dynamics in a 2D external flow.
- Identification of dimensionless parameters governing vesicle motion.
- Characterization of transitions using bifurcation theory (saddle-node and Hopf).
Main Results:
- Vesicle dynamics are dictated by two dimensionless parameters related to fluid properties, membrane characteristics, and flow conditions.
- Transitions from tank-treading to tumbling occur via saddle-node bifurcation.
- Transitions from tank-treading to trembling occur via Hopf bifurcation.
- A slowdown in vesicle dynamics is observed near the transition lines, following power laws with exponents 1/4 and 1/2 for tumbling and trembling, respectively.
Conclusions:
- The study provides a comprehensive framework for understanding vesicle dynamics in 2D flows.
- The identified critical exponents offer insights into the universal behavior of systems near phase transitions.
- The findings contribute to the fundamental understanding of soft matter behavior in complex flows.
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