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Viscosity kernel of molecular fluids: butane and polymer melts
R M Puscasu1, B D Todd, P J Daivis
1Centre for Molecular Simulation, Swinburne University of Technology, PO Box 218, Hawthorn, Victoria 3122, Australia. rpuscasu@swin.edu.au
Physical Review. E, Statistical, Nonlinear, and Soft Matter Physics
|September 28, 2010
Summary
We determined wave-vector dependent shear viscosities for molecular fluids. Fluid density significantly impacts viscosity kernel shape, crucial for understanding nanoscale flow properties.
Area of Science:
- Chemical Physics
- Fluid Dynamics
- Materials Science
Background:
- Understanding the shear viscosity of molecular fluids is crucial for predicting their flow behavior.
- Existing hydrodynamic models often assume local equilibrium, which may not hold at nanoscale.
Purpose of the Study:
- To determine wave-vector dependent shear viscosities for butane and freely jointed chains.
- To investigate the influence of density, temperature, and chain length on viscosity kernels.
- To assess the applicability of generalized hydrodynamics for molecular fluids.
Main Methods:
- Equilibrium molecular dynamics simulations were employed.
- Both atomic and molecular hydrodynamic formalisms were used.
- Transverse momentum density and stress autocorrelation functions were calculated.
Main Results:
- The density was found to significantly affect the shape of the viscosity kernel.
- Temperature and chain length had a lesser impact on the normalized kernel shape.
- Functional forms fitting the wave-vector dependent kernel data were tested.
- The real-space viscosity kernel width is approximately 3-6 atomic diameters.
Conclusions:
- Generalized hydrodynamics is necessary for predicting molecular fluid flow properties at the nanoscale.
- The findings are relevant for applications in nanofluidics and microfluidics.
- The study provides insights into the relationship between molecular structure and macroscopic fluid behavior.
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