Duality of diffusion dynamics in particle motion in soft-mode turbulence

Area of Science:

• Soft Matter Physics
• Nonlinear Dynamics
• Liquid Crystal Physics

Background:

• Conventional Brownian motion describes random particle movement due to thermal fluctuations.
• Soft-mode turbulence (SMT) in nematic liquid crystals exhibits complex spatiotemporal dynamics.
• Understanding particle diffusion in turbulent environments is crucial for various physical phenomena.

Purpose of the Study:

• To experimentally investigate nonthermal Brownian motion in soft-mode turbulence (SMT).
• To characterize particle dynamics and diffusion mechanisms within SMT.
• To develop a simplified model explaining short-time and asymptotic diffusion behaviors.

Main Methods:

• Injecting tracer particles into electroconvection-driven SMT in a nematic liquid crystal.
• Classifying particle motion into fast (local flow) and slow (global pattern) phases.
• Developing a simplified model to estimate correlation time and analyze diffusion.

Main Results:

• Particle motion in SMT exhibits two distinct phases: fast and slow.
• The SMT pattern correlation time scales as τ(d)∼ɛ(-1), derived from particle dynamics.
• A non-Gaussian displacement distribution in the short-time regime was observed and modeled.

Conclusions:

• Particle diffusion in SMT differs significantly from conventional Brownian motion.
• The study provides insights into the mechanisms governing diffusive motion in complex fluid systems.
• The findings validate a simplified model and offer a new perspective on nonthermal diffusion.