Dynamics of a multicomponent vesicle in shear flow

TL;DR

This paper investigates the complex nonlinear dynamics of multicomponent vesicles in shear flow, revealing novel phase-treading and tumbling behaviors caused by inhomogeneous bending, which differ from classical homogeneous vesicle dynamics.

Contribution

It introduces a detailed numerical analysis of multicomponent vesicle dynamics, uncovering new oscillatory and tumbling mechanisms driven by material heterogeneity.

Findings

Discovery of phase-treading and tumbling mechanisms in multicomponent vesicles.

Unsteady periodic dynamics with oscillatory inclination angle.

Tumbling occurs at low shear rates when phase concentration is around 1/2.

Abstract

We study the fully nonlinear, nonlocal dynamics of two-dimensional multicomponent vesicles in a shear flow with matched viscosity of the inner and outer fluids. Using a nonstiff, pseudo-spectral boundary integral method, we investigate dynamical patterns induced by inhomogeneous bending for a two phase system. Numerical results reveal that there exist novel phase-treading and tumbling mechanisms that cannot be observed for a homogeneous vesicle. In particular, unlike the well-known steady tank-treading dynamics characterized by a fixed inclination angle, here the phase-treading mechanism leads to unsteady periodic dynamics with an oscillatory inclination angle. When the average phase concentration is around 1/2, we observe tumbling dynamics even for very low shear rate, and the excess length required for tumbling is significantly smaller than the value for the single phase case. We summarize our results in phase diagrams in terms of the excess length, shear rate, and concentration of the soft phase. These findings go beyond the well known dynamical regimes of a homogeneous vesicle and highlight the level of complexity of vesicle dynamics in a fluid due to heterogeneous material properties.