Effect of thermal noise on vesicles and capsules in shear flow

TL;DR

This paper investigates how thermal noise influences the dynamics of vesicles and capsules in shear flow, revealing new regimes and behaviors through analytical stochastic modeling.

Contribution

It introduces a consistent way to incorporate thermal noise into reduced models and derives phase diagrams showing new dynamical regimes.

Findings

Thermal fluctuations induce tumbling at small shear rates for vesicles.

An intermittent regime appears in elastic capsules due to thermal mixing.

Thermal noise causes qualitative changes in the dynamical behavior of vesicles and capsules.

Abstract

We add thermal noise consistently to reduced models of undeformable vesicles and capsules in shear flow and derive analytically the corresponding stochastic equations of motion. We calculate the steady-state probability distribution function and construct the corresponding phase diagrams for the different dynamical regimes. For fluid vesicles, we predict that at small shear rates thermal fluctuations induce a tumbling motion for any viscosity contrast. For elastic capsules, due to thermal mixing, an intermittent regime appears in regions where deterministic models predict only pure tank treading or tumbling.