Dynamic contact angles and spreading on a flat plate at moderately low velocities

Area of Science:

• Fluid dynamics
• Interface science
• Soft matter physics

Background:

• Dynamic contact lines are crucial in fluid displacement phenomena.
• Classical models predict singularities, necessitating advanced theoretical approaches.
• Understanding microscopic physics at interfaces is key to accurate predictions.

Purpose of the Study:

• To analyze the flow field near dynamic contact lines in liquid-liquid systems.
• To develop and validate a robust theoretical framework for dynamic wetting.
• To investigate the interplay between macroscopic hydrodynamics and microscopic physics.

Main Methods:

• Asymptotic expansion to O(U^2) for small substrate velocities.
• Regularization of stress singularity using a molecular-scale cutoff.
• Systematic comparison of theoretical predictions with experimental data.

Main Results:

• A robust and versatile framework for describing dynamic wetting behavior was established.
• The molecular-scale cutoff model shows excellent agreement with experimental data.
• Singular perturbation theory successfully bridges continuum hydrodynamics with equilibrium, yielding microscopic physics parameters.

Conclusions:

• The study provides new insights into the physics of moving contact lines.
• The developed framework accurately predicts wetting rates and interfacial forces.
• This work unifies continuum hydrodynamics with microscopic physics for dynamic wetting phenomena.