Molecular and continuum boundary conditions for a miscible binary fluid.

Area of Science:

• Physics
• Physical Chemistry
• Materials Science

Background:

• Continuum equations and molecular dynamics are used to model fluid behavior.
• Boundary conditions at solid-fluid interfaces are crucial for accurate simulations.
• Previous studies have explored fluid behavior at the nanoscale.

Purpose of the Study:

• To investigate the utility of molecular-dynamics simulations for establishing boundary conditions at solid-fluid interfaces.
• To reconcile nanoscale simulation results with continuum fluid dynamics.
• To explore novel fluid behaviors driven by concentration gradients and differential wetting.

Main Methods:

• Conducting molecular-dynamics simulations of a two-component fluid at a solid surface.
• Analyzing convective-diffusive flow and concentration gradients at atomic scales.
• Comparing simulation results with established continuum equations, including the Navier slip condition.

Main Results:

• Molecular-dynamics simulations successfully provide boundary conditions for two-component fluids at solid surfaces.
• Convective-diffusive flow aligns with continuum equations down to atomic scales.
• Concentration gradients can induce flow without viscous dissipation, diverging from the Navier slip condition.
• Differential wetting and concentration gradients can generate convective flows.

Conclusions:

• Molecular-dynamics simulations are valuable for defining nanoscale boundary conditions in fluid dynamics.
• Observed phenomena challenge the universal applicability of the Navier slip condition.
• The coupling of differential wetting and concentration gradients offers potential for developing nanoscale devices like nanopumps and motors.