Hydrodynamic interactions between two equally sized spheres in viscoelastic fluids in shear flow
Frank Snijkers1, Rossana Pasquino, Jan Vermant
1Department of Chemical Engineering, University of Leuven (KULeuven), Leuven, Belgium. frank.snijkers@gmail.com
Langmuir : the ACS Journal of Surfaces and Colloids
|April 23, 2013
Summary
This study investigated how different fluids affect sphere interactions in shear flow. Shear-thinning viscosity was found to be key in determining interaction behavior and flow-induced assembly.
Area of Science:
- Fluid Dynamics
- Rheology
- Soft Matter Physics
Background:
- Understanding flow-induced assembly of particles is crucial in various scientific fields.
- Hydrodynamic interactions govern particle behavior in fluid flows.
- The role of viscoelasticity in particle dynamics remains an active area of research.
Purpose of the Study:
- To experimentally investigate the in-plane hydrodynamic interaction between two spheres in shear flow.
- To determine the effect of viscoelastic suspending media on flow-induced assembly, specifically string formation.
- To elucidate the relationship between fluid rheological properties and particle trajectory patterns.
Main Methods:
- Utilized a counterrotating device with Couette geometry for controlled shear flow.
- Employed quantitative videomicroscopy for precise tracking of sphere movement.
- Tested four distinct suspending media: Newtonian fluid, Boger fluid, wormlike micellar solution, and shear-thinning elastic polymer solution.
Main Results:
- Newtonian fluid interactions showed symmetric trajectories.
- Boger fluid interactions maintained planar trajectories but lacked symmetry.
- Wormlike micellar and shear-thinning elastic solutions exhibited highly asymmetric interactions with reversing and open trajectories.
- Trajectory type depended on initial sphere configuration and shear rate.
Conclusions:
- Shear-thinning viscosity is the primary rheological factor governing sphere interaction nature.
- Normal stress differences are less critical than shear-thinning in determining interaction outcomes.
- Findings provide insights into controlling flow-induced particle assembly through fluid selection.
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