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Analyzing Melts and Fluids from Ab Initio Molecular Dynamics Simulations with the UMD Package

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Parameterization of the nonlocal viscosity kernel for an atomic fluid.

J S Hansen¹, Peter J Daivis, Karl P Travis

¹Centre for Molecular Simulation, Swinburne University of Technology, P.O. Box 218, Hawthorn, Victoria 3122, Australia. jhansen@ict.swin.edu.au

Physical Review. E, Statistical, Nonlinear, and Soft Matter Physics

|November 13, 2007

Summary

This study presents wave-vector dependent shear viscosity for atomic fluids using molecular dynamics. Results show generalized hydrodynamic relations are needed for nanofluidic flows due to the viscosity kernel

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Area of Science:

Computational physics
Fluid dynamics
Materials science

Background:

Understanding shear viscosity is crucial for fluid dynamics.
Generalized hydrodynamic relations are necessary when fluid properties vary significantly over short distances.

Purpose of the Study:

To compute and analyze wave-vector dependent shear viscosity for a model atomic fluid.
To investigate the applicability of generalized hydrodynamic constitutive relations in nanofluidic flows.

Main Methods:

Molecular dynamics simulations were employed to compute shear viscosity.
The wave-vector dependent shear viscosity data was fitted to Gaussian and Lorentzian functions.
Density dependencies of the fitting parameters were analyzed.

Main Results:

The shear viscosity data was successfully fitted using two functional forms: a two-Gaussian function and a Lorentzian function.
The Lorentzian function provided a better fit over the studied range of wave vectors and densities.
The real space viscosity kernel was found to have a width of 2 to 3 atomic diameters.

Conclusions:

The computed shear viscosity data exhibits simple density dependencies for both fitting functions.
The significant width of the real space viscosity kernel necessitates the use of generalized hydrodynamic constitutive relations for analyzing nanofluidic flows.