Dynamic phase separation: from coarsening to turbulence via structure formation

Area of Science:

• Physics
• Materials Science
• Fluid Dynamics

Background:

• Cahn-Hilliard models describe phase separation in materials.
• Hydrodynamic motion can be driven by concentration gradients (buoyancy, Marangoni effect).
• Previous studies explored one-dimensional driven systems.

Purpose of the Study:

• Investigate new two-dimensional convective Cahn-Hilliard models.
• Analyze the transition from coarsening to irregular dynamics.
• Understand the role of driving force on phase separation.

Main Methods:

• Numerical study of three models: local scalar, nonlocal scalar, and vector order parameter.
• Analysis of system behavior under varying driving force intensities.
• Comparison with the Kuramoto-Sivashinsky equation.

Main Results:

• Observed transition from coarsening to spatiotemporally irregular behavior (turbulence).
• Formation of spatial patterns at intermediate driving intensities.
• Driving force breaks phase symmetry and increases coarsening rate.
• Coarsening stops at higher driving forces; dynamics become irregular but structured.

Conclusions:

• New 2D convective Cahn-Hilliard models exhibit complex dynamics.
• Driving force significantly influences phase separation and introduces turbulence.
• The transition to turbulence is mediated by pattern formation.