Impact of random nanoscale roughness on gas-scattering dynamics

Area of Science:

• Physics
• Materials Science
• Chemical Engineering

Background:

• Nanoscale wall roughness significantly impacts rarefied gas transport.
• Scattering dynamics at the gas-surface interface remain poorly understood.

Purpose of the Study:

• Develop a novel scattering kernel to model gas-surface interactions on nanoscale rough surfaces.
• Characterize distinct interaction types: gas-phonon collisions and hard collisions due to surface irregularities.

Main Methods:

• Incorporated a pseudo Debye-Waller factor to transition between smooth and rough surface models.
• Validated the scattering kernel using high-fidelity molecular dynamics simulations.
• Tested across varying roughness, temperature, and gas-surface combinations.

Main Results:

• The model accurately captures scattering dynamics for gas molecular beams at different velocities.
• Achieved precise predictions for accommodation coefficients and reflection patterns.
• Successfully predicted macroscopic quantities like velocity slip and temperature jumps.

Conclusions:

• The developed scattering kernel effectively models gas-surface interactions on rough surfaces.
• Provides accurate predictions for both molecular scattering and macroscopic transport phenomena.
• Offers a valuable tool for understanding and engineering systems involving rarefied gas flows.