Dynamics of chiral liquid crystals between cylinders using Landau-de Gennes theory

• Published in: Liquid crystals 2023-02, Vol.50 (3), p.437-452
• Main Authors: Nikzad, Arash, Grecov, Dana
• Format: Article
• Language: English
• Subjects: Chiral liquid crystals; chiral strength; Chirality; concentric and eccentric cylinders; Crystals; Cylinders; Deborah number; Eccentricity; Landau-de Gennes theory; Liquid crystals; Lubricants; Microstructure; Nonuniformity; shear flow
• ISSN: 0267-8292; 1366-5855
• DOI: 10.1080/02678292.2022.2135035

This study employs the Landau-de Gennes theory to investigate the behaviour of chiral liquid crystals (CLCs) between concentric and eccentric cylinders under different flow conditions. This theory was implemented in dynamic finite element simulations to solve the evolution of the microstructure of CLCs and couple it with linear momentum balance equation (modified Navier-Stokes equation) to capture the structure of CLCs. The study focused on the microstructure formation of CLCs and their performance as lubricants under various chirality strengths (θ), Deborah numbers (De), and eccentricity of eccentric cylinders. The hexagonal structure of the CLCs was found between cylinders at low De (0.001), where the chiral term predominates. Moreover, the number of hexagonal structures between cylinders was shown to be significantly correlated to the chiral strength. We showed that increasin De resulted in vanishing hexagonal pattern of CLCs and the De value at which the hexagonal pattern vanishes depends on the chiral strength. We also observed that a higher eccentricity ratio significantly increased the pressure force per length on the inner cylinders and caused more non-uniformity in the structure. Based on the findings, we concluded that the performance of CLCs as lubricants is greater at higher θ and eccentricity and lower De.