Mass and momentum transfer across solid-fluid boundaries in the lattice-Boltzmann method

Area of Science:

• Computational Fluid Dynamics
• Numerical Methods
• Physics

Background:

• Mass and momentum transfer at solid-fluid boundaries are critical in lattice-Boltzmann method (LBM) development.
• Existing LBM treatments often enforce local mass conservation, which may be unnecessary.

Purpose of the Study:

• To review and challenge the necessity of preventing net mass transfer across solid-fluid boundaries in LBM.
• To investigate the impact of local mass conservation constraints on simulation accuracy.

Main Methods:

• Designed simulations to analyze boundary movement, density gradients, and grid resolution effects.
• Examined the consequences of local versus global mass conservation in LBM.

Main Results:

• Global mass conservation is achievable even with local imbalances at boundary nodes.
• Implementing local mass conservation constraints leads to erroneous flow and pressure fields.
• Concerns regarding momentum addition/reduction at status-changing nodes are often technically unnecessary.

Conclusions:

• Local mass conservation is not required for global mass conservation in LBM and can be detrimental.
• The study clarifies that local constraints are harmful for accurate simulation results.
• Momentum transfer considerations at status-changing nodes do not directly impact flow fields but can affect particulate suspension simulations.