Evaluation of a lattice Boltzmann method in a complex nanoflow

Area of Science:

• Computational fluid dynamics
• Fluid mechanics
• Nanoscale transport phenomena

Background:

• Simulating complex fluid flows across continuum to transitional regimes requires efficient methods.
• The lattice Boltzmann method (LBM) offers a promising approach for such simulations.
• Previous work established an LBM with specific boundary conditions and relaxation times.

Purpose of the Study:

• To assess the performance of a specific lattice Boltzmann method (LBM).
• To evaluate the regularization procedure and third-order truncation of a D2Q21 LBM model.
• To validate the LBM against molecular dynamics simulations for complex flow cases.

Main Methods:

• Utilized a lattice Boltzmann method (LBM) with diffuse scattering wall boundary conditions.
• Employed a regularization procedure and an effective relaxation time dependent on the Knudsen number.
• Performed simulations for Poiseuille flows, Couette flows, and flow around a square cylinder in a nanochannel.
• Conducted molecular dynamics simulations for reference data of the square cylinder flow.

Main Results:

• The third-order truncated D2Q21 LBM accurately predicted flow profiles and slip velocities for Poiseuille and Couette flows.
• The second-order truncated D2Q9 LBM adequately predicted velocity profiles around a square cylinder.
• The absence of the regularization process led to unphysical momentum oscillations in flow field predictions.

Conclusions:

• The regularization procedure is essential for accurate LBM simulations, particularly around geometric features.
• Both second and third-order truncated LBM models show utility depending on the flow complexity.
• The evaluated LBM provides a cost-effective strategy for simulating complex flows in various regimes.