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Shear-stress-controlled dynamics of nematic complex fluids.
Sabine H L Klapp1, Siegfried Hess
1Institut für Theoretische Physik, Sekretariat EW 7-1, Technische Universität Berlin, Hardenbergstrasse 36, D-10623 Berlin, Germany.
Physical Review. E, Statistical, Nonlinear, and Soft Matter Physics
|September 28, 2010
Summary
Investigating sheared nematic liquids using mesoscopic theory, this study reveals distinct nonequilibrium dynamics under stress control compared to shear rate control. Stress control simplifies transitions, stabilizing chaotic states.
Area of Science:
- Nonlinear dynamics
- Soft matter physics
- Liquid crystal theory
Background:
- Nematic liquid crystals exhibit complex nonequilibrium dynamics when subjected to shear.
- Traditional studies often use shear rate as the control parameter, limiting exploration of stress-driven phenomena.
Purpose of the Study:
- To investigate the nonequilibrium dynamics of sheared nematic liquids under shear stress control.
- To compare stress-controlled dynamics with shear rate-controlled dynamics.
- To explore the influence of control parameter choice on dynamic transitions and stability.
Main Methods:
- Mesoscopic theory framework.
- Supplementing orientational order parameter equations with an equation for time-dependent shear rate.
- Analysis of system behavior under controlled shear stress (σ xy) versus controlled shear rate (γ).
Main Results:
- Stress-controlled flow properties are similar to shear rate-controlled ones when starting from an isotropic state.
- Significant differences emerge for nematic equilibrium states, with stress control showing a single transition to a stationary state.
- Chaotic regimes observed under shear rate control can be stabilized by switching to stress control.
Conclusions:
- Shear stress control offers a simplified yet tunable pathway to understand nematic liquid crystal dynamics.
- The choice of control parameter profoundly impacts the observed nonequilibrium transitions and accessible dynamic states.
- Delay time in stress control and method switching are key factors for stabilizing complex dynamics.
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