Droplet morphologies on particles with macroscopic surface roughness

Area of Science:

• Surface science
• Fluid dynamics
• Computational physics

Background:

• Understanding liquid droplet behavior on solid surfaces is crucial in various fields.
• Macroscopic surface roughness significantly impacts wetting phenomena.
• Predicting droplet configuration on rough particles requires advanced simulation techniques.

Purpose of the Study:

• To determine the equilibrium configuration of liquid droplets on macroscopically rough solid particles.
• To investigate the influence of droplet size, contact angle, and surface roughness on fractional surface coverage.
• To analyze the effect of droplet coalescence on surface coverage variations.

Main Methods:

• Numerical simulations were performed using the volume-of-fluid (VOF) method.
• Systematic investigation of fractional surface coverage as a function of key parameters.
• Analysis of droplet behavior including coalescence.

Main Results:

• Fractional surface coverage is primarily governed by droplet size and equilibrium contact angle.
• Particle surface roughness (amplitude and correlation length) has a lesser effect on surface coverage compared to droplet size and contact angle.
• Droplet coalescence leads to significant variations in surface coverage, especially at larger contact angles.

Conclusions:

• Droplet size and contact angle are dominant factors controlling liquid distribution on rough particles.
• Surface roughness plays a secondary role in determining equilibrium droplet configuration.
• Coalescence introduces variability in surface coverage, highlighting the complexity of multiphase flow on rough surfaces.