Contact Angle Measurement on Curved Wetting Surfaces in Multiphase Lattice Boltzmann Method.

Area of Science:

• Computational physics
• Fluid dynamics
• Surface science

Background:

• Contact angle is crucial for understanding wettability, capillary phenomena, and moving contact lines.
• Current experimental and simulation methods for contact angle measurement are often complex and time-consuming.
• Accurate measurement of contact angles, especially on curved surfaces, remains a challenge.

Purpose of the Study:

• To develop an efficient and accurate scheme for measuring contact angles on curved wetting surfaces using lattice Boltzmann simulations.
• To validate the proposed scheme against theoretical predictions and experimental observations.
• To demonstrate the scheme's applicability to dynamic contact angle hysteresis and moving contact lines.

Main Methods:

• Implementation of a novel contact angle measurement scheme within the lattice Boltzmann simulation framework.
• Grid-independent simulations were performed with varying drop sizes and surface curvatures.
• Verification of the scheme in gravitational environments by simulating sessile and pendent droplet deformations.
• Application of the scheme to analyze dynamic contact angle hysteresis on homogeneous and heterogeneous curved surfaces.

Main Results:

• The measurement results showed excellent agreement with theoretical predictions, independent of gravity.
• The scheme was confirmed to be grid-independent across various simulation parameters.
• Numerical results closely matched experimental observations, supporting the theory of gravity-independent microscopic contact angles.
• The method successfully captured dynamic contact angle hysteresis on different surface types.

Conclusions:

• The developed scheme provides a simple, efficient, and accurate method for measuring contact angles on curved surfaces in lattice Boltzmann simulations.
• The technique is versatile, applicable to non-axisymmetric shapes, moving contact lines, and dynamic phenomena like contact angle hysteresis.
• This accurate measurement capability facilitates dynamic mechanical analysis of moving contact lines and can be extended to various multiphase lattice Boltzmann models.