Odd Viscosity in Chiral Passive Suspensions

TL;DR

This paper demonstrates that suspensions of chiral-shaped particles exhibit odd viscosity and complex stress behaviors similar to active fluids, even without external driving or activity.

Contribution

It reveals the existence of odd viscosity in passive, chirally-shaped particle suspensions through computational simulations, expanding understanding beyond active fluids.

Findings

Ratchet suspensions have intermediate shear and extensional viscosities.

They exhibit nonzero even and odd components of the first normal stress coefficient.

The behavior combines features of complex fluids and chiral viscous fluids.

Abstract

Prior studies have revealed that nonzero odd viscosity is an essential property for chiral active fluids. Here we report that such an odd viscosity also exists in suspensions of non-active or non-externally-driven but chirally-shaped particles. Computational simulations are carried out for monolayers of dense ratchets in simple shear and planar extensional flows. The contact between two ratchets can be either frictionless or infinitely-frictional, depending on their teeth and sliding directions at the contact point. Our results show that the ratchet suspension has the intermediate shear/extensional viscosity as compared with the suspensions of smooth and gear-like particles. Meanwhile, the ratchet suspensions show nonzero even and odd components of the first normal stress coefficient, which indicates the mixed feature of conventional complex fluids and chiral viscous fluids.