From Equilibrium Multistability to Spatiotemporal Chaos in Channel Flows of Nematic Fluids

TL;DR

This paper explores how pressure-driven flows in nematic liquid crystals confined in channels lead to multistability, complex dynamics, and spatiotemporal chaos, revealing new nonequilibrium behaviors influenced by scalar order variations.

Contribution

It demonstrates the emergence of multistability and chaotic regimes in nematic channel flows using the Beris-Edwards model, highlighting effects not captured by simpler models.

Findings

Multiple coexisting steady states identified

Transition to unsteady and chaotic flows with increasing pressure

Predictions of defect dynamics and turbulence in nematic flows

Abstract

We investigate channel-confined, nematic liquid crystals using the Beris-Edwards model of nematohydrodynamics. Using strong homeotropic anchoring at the walls, we find multistability i.e. multiple coexisting states where the uniform nematic state coexists with states having spatially varying scalar nematic order and director fields. When a pressure gradient is applied, flows develop, and the inherent multistability of the system organizes a variety of complex dynamics. For low pressure gradients, steady flows are established, and the director fields that emerge from the multistable states at equilibrium correspond to Bowser and Dowser configurations similar to those reported in experiments. An increasing pressure-gradient destabilizes steady Bowser and Dowser flow states sequentially, leading to unsteady periodic and chaotic regimes featuring cyclical topological transitions, pulsating flows, advecting defects and spatiotemporal chaos. These findings demonstrate that modest variations in the scalar nematic order, as captured by the Beris-Edwards model, can qualitatively modify equilibrium structures and give rise to complex nonequilibrium behaviour in confined nematics-contrasting with the Ericksen-Leslie model, which assumes a constant scalar order parameter. Our key model predictions - multistability, periodically oscillating states and advecting defect-mediated turbulence can be experimentally investigated in pressure-driven channel flows of nematic fluids.