Viscosity of a binary mixture: approach to the hydrodynamic limit
Mathieu G McPhie1, Peter J Daivis, Ian K Snook
1Applied Physics, School of Applied Sciences, RMIT University, GPO Box 2476V, Melbourne, Victoria 3001, Australia. m.mcphie@fz-juelich.de
Physical Review. E, Statistical, Nonlinear, and Soft Matter Physics
|October 10, 2006
Summary
Molecular dynamics simulations reveal how nanocolloidal particle properties affect solution viscosity and self-diffusion. Increased particle concentration or size dramatically enhances shear thinning, impacting fluid behavior.
Area of Science:
- Colloid Science
- Computational Physics
- Materials Science
Background:
- Understanding the rheological properties of colloidal suspensions is crucial for various industrial applications.
- Nanocolloidal particle behavior in solutions is influenced by factors like size, mass, and concentration.
Purpose of the Study:
- To investigate the solute self-diffusion coefficient and shear rate-dependent viscosity in model nanocolloidal solutions.
- To determine the impact of mass ratio, size ratio, and concentration on these properties.
Main Methods:
- Employed equilibrium and nonequilibrium molecular dynamics simulations.
- Studied model nanocolloidal particles with varying mass ratios (μ=1 to 50) and size ratios (s=1 to 4.03).
- Analyzed data in the strongly shear-thinning regime for suspensions with Newtonian or weakly shear-thinning solvents.
Main Results:
- Shear thinning rate increased significantly with solute volume fraction, irrespective of whether it was due to size or concentration.
- Viscosities and self-diffusion coefficients approached mass ratio-independent values exponentially.
- Calculated hydrodynamic radius (RH) using various methods, showing consistency and indicating slip boundary conditions.
Conclusions:
- Solute volume fraction is a dominant factor in shear thinning behavior.
- The hydrodynamic radius is slightly smaller than the cross-interaction radius.
- Simulation results provide insights into nanocolloidal suspension dynamics and rheology.
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