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Shear-induced instabilities in layered liquids.
Günter K Auernhammer1, Helmut R Brand, Harald Pleiner
1Theoretische Physik III, Universität Bayreuth, 95440 Bayreuth, Germany. guenter.auernhammer@uni-bayreuth.de
Summary
Shear stress can destabilize smectic-A liquid crystals. This study reveals how director and layer normal misalignment causes undulation instability, matching experimental observations.
Area of Science:
- Soft Matter Physics
- Liquid Crystal Hydrodynamics
- Rheology
Background:
- Smectic-A systems exhibit shear-induced destabilization and reorientation.
- Existing hydrodynamic models may not fully capture complex nonequilibrium behaviors.
Purpose of the Study:
- To develop an extended hydrodynamic formulation for smectic-A systems under shear.
- To investigate the coupling between nematic director and smectic layering.
- To analyze the resulting undulation instability.
Main Methods:
- Macroscopic hydrodynamic description including layer displacement and director orientation.
- Analysis of director-nematic coupling under simple shear.
- Mathematical modeling of effective layer dilatation and instability thresholds.
Main Results:
- A finite angle between director and layer normal arises from shear, equivalent to effective layer dilatation.
- This dilatation triggers an undulation instability above a critical threshold.
- Cross-couplings with velocity and order parameters influence instability dynamics.
Conclusions:
- The extended model explains shear-induced undulation instability in smectic-A systems.
- Results show good qualitative agreement with recent experiments and simulations.
- Understanding these instabilities is crucial for predicting material behavior under flow.