The role of fluid flow in the dynamics of active nematic defects

Abstract

We adapt the Halperin-Mazenko formalism to analyze two-dimensional active nematics coupled to a generic fluid flow. The governing hydrodynamic equations lead to evolution laws for nematic topological defects and their corresponding density fields. We find that $\pm 1/2$ defects are propelled by the local fluid flow and by the nematic orientation coupled with the flow shear rate. In the overdamped and compressible limit, we recover the previously obtained active self-propulsion of the +1/2 defects. Non-local hydrodynamic effects are primarily significant for incompressible flows, for which it is not possible to eliminate the fluid velocity in favor of the local defect polarization alone. For the case of two defects with opposite charge, the non-local hydrodynamic interaction is mediated by non-reciprocal pressure-gradient forces. Finally, we derive continuum equations for a defect gas coupled to an arbitrary (compressible or incompressible) fluid flow.

References in corpus (5)

• Spontaneous motion in hierarchically assembled active matter
• Minimal model for active nematics: quasi-long-range order and giant fluctuations
• Defect dynamics in active nematics
• Orientation of topological defects in 2D nematic liquid crystals
• Memory effects, arches and polar defect ordering at the cross-over from wet to dry active nematics

Cited by in corpus (15)

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• Design rules for controlling active topological defects
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• A unified field theory of topological defects and non-linear local excitations
• Kinematics and dynamics of disclination lines in three-dimensional nematics
• Defect Loops in Three-Dimensional Active Nematics as Active Multipoles
• Defect dynamics in active smectics induced by confining geometry and topology
• Traction and Stress Control Formation and Motion of +1/2 Topological Defects in Epithelial Cell Monolayers
• Active Nematic Multipoles: Flow Responses and the Dynamics of Defects and Colloids
• A computational study of nematic core structure and disclination interactions in elastically anisotropic nematics
• Analytical model for the motion and interaction of two-dimensional active nematic defects
• Topological defects in polar active matter
• Defect configuration of an active nematic around a circular obstacle
• Defect Interactions Through Periodic Boundaries in Two-Dimensional $p$-atics