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Updated: Jul 18, 2026
08:01
The Diffusion of Passive Tracers in Laminar Shear Flow
Published on: May 1, 2018
Tracer diffusion in hard sphere fluids from molecular to hydrodynamic regimes
R O Sokolovskii1, M Thachuk, G N Patey
1Department of Chemistry, University of British Columbia, Vancouver, British Columbia V6T 1Z1, Canada.
The Journal of Chemical Physics
|December 6, 2006
Summary
Finite-size effects in molecular dynamics simulations can underestimate tracer diffusion constants. Extrapolation methods overcome this, yielding accurate infinite-volume estimates consistent with theoretical predictions.
Area of Science:
- Computational physics
- Statistical mechanics
- Fluid dynamics
Background:
- Understanding tracer diffusion in fluids is crucial for various scientific fields.
- Molecular dynamics simulations are a powerful tool for studying particle transport at the microscopic level.
- Finite-size effects in simulations can introduce significant errors in diffusion measurements.
Purpose of the Study:
- To investigate tracer diffusion in hard sphere fluids using molecular dynamics.
- To identify and overcome finite-size effects in simulation results.
- To compare simulation data with theoretical predictions in different diffusion regimes.
Main Methods:
- Molecular dynamics simulations were performed for hard sphere fluids.
- A range of reduced densities (0.02 to 0.52) and tracer sizes (0.125σ to 16σ) were explored.
- A linear extrapolation formula based on reciprocal cell length was applied to correct for finite-size effects.
Main Results:
- Finite-size effects were found to significantly underestimate tracer diffusion constants.
- Extrapolation to infinite volume provided accurate diffusion estimates across all tracer sizes.
- Extrapolated results in the hydrodynamic limit matched theoretical slip boundary conditions.
Conclusions:
- A robust extrapolation method is essential for accurate tracer diffusion studies in molecular dynamics.
- The study validates theoretical predictions of slip boundary conditions in the hydrodynamic regime.
- A new expression is proposed to accurately model diffusion behavior across densities and tracer sizes.
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