Colloidal clustering and diffusion in a convection cell array.

Area of Science:

• Fluid dynamics
• Statistical physics
• Soft matter physics

Background:

• Understanding particle behavior in fluid flows is crucial for various applications.
• Convection cells create complex flow patterns that influence particle dynamics.
• Steric interactions between particles play a significant role in collective behavior.

Purpose of the Study:

• To numerically investigate the clustering of finite-size disks in a 2D convection cell array.
• To analyze the formation of spatial structures and their dependence on system parameters.
• To examine the mechanisms driving particle diffusion and their robustness against noise.

Main Methods:

• Numerical simulations of disk suspensions in a linear array of 2D convection cells.
• Analysis of particle trajectories, spatial arrangements, and collision events.
• Investigation of the effects of steric interactions, advection, and pair collisions.

Main Results:

• Disks form coherently rotating structures at cell centers driven by advection and collisions.
• Micellar, ring-like, and hexatic patterns emerge in the deterministic regime but dissolve with thermal fluctuations.
• Particle collisions induce athermal diffusion, enabling cell crossings even in the absence of thermal noise.

Conclusions:

• Steric interactions and flow advection are key drivers of pattern formation in confined particle suspensions.
• Athermal diffusion is a significant phenomenon in noiseless systems, driven by inter-particle collisions.
• The study highlights the interplay between deterministic forces and thermal noise in dictating particle suspension dynamics.