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Generation and Control of Electrohydrodynamic Flows in Aqueous Electrolyte Solutions
Published on: September 7, 2018
Non-Newtonian stress in an electrolyte
1Department of Applied Mathematics and Theoretical Physics, University of Cambridge, Cambridge, UK. jds60@cam.ac.uk
The Journal of Physical Chemistry. B
|January 12, 2011
Summary
This study reveals that the electrical contribution to viscosity in charged colloidal suspensions exhibits shear thinning and elastic properties. These effects become significant at very high shear rates, impacting fluid dynamics.
Area of Science:
- Physical Chemistry
- Fluid Dynamics
- Colloid Science
Background:
- Electrolyte solutions and charged colloidal suspensions share dynamic similarities.
- Viscosity in both systems depends on ionic concentration and the Peclet number (Pe).
- The Peclet number quantifies the balance between shear rate deformation and diffusive relaxation of ionic charge clouds.
Purpose of the Study:
- To explore the rheological behavior of dilute charged colloidal suspensions.
- To investigate the shear-thinning and elastic properties of the electrical contribution to viscosity.
- To analyze the appearance of normal stress differences at higher Peclet numbers.
Main Methods:
- Drawing analogies between electrolyte dynamics and colloidal suspension behavior.
- Applying previously published results on colloidal suspension rheology (Lever, 1979).
- Analyzing the implications of these results for the Falkenhagen electrical contribution to viscosity.
Main Results:
- The Falkenhagen electrical contribution to viscosity (scaling as O(c(1/2))) demonstrates shear thinning.
- This electrical contribution to stress is elastic, leading to normal stress differences at O(Pe(2)).
- Significant deviations from Newtonian rheology require extremely high shear rates (around 10^9 s^-1).
Conclusions:
- The rheology of charged colloidal suspensions is analogous to electrolyte solutions, exhibiting complex shear-dependent behavior.
- Elasticity and shear thinning are inherent properties of the electrical contribution to viscosity in these systems.
- Understanding these phenomena requires considering high shear rates where non-Newtonian effects dominate.
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