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11:03
An Analog Macroscopic Technique for Studying Molecular Hydrodynamic Processes in Dense Gases and Liquids
Published on: December 4, 2017
Hydrodynamic stress on small colloidal aggregates in shear flow using Stokesian dynamics.
Ryohei Seto1, Robert Botet, Heiko Briesen
1Chair for Process Systems Engineering, Technische Universität München, Weihenstephaner Steig 23, D-85350 Freising, Germany. setoryohei@me.com
Physical Review. E, Statistical, Nonlinear, and Soft Matter Physics
|December 21, 2011
Summary
Rigid fractal aggregates in shear flow exhibit predictable hydrodynamic properties. Their drag force distributions collapse onto a master curve, explaining stress behaviors and predicting restructuring in colloidal systems.
Area of Science:
- Fluid dynamics
- Colloidal science
- Materials science
Background:
- Fractal aggregates are common in colloidal systems.
- Understanding their hydrodynamic properties is crucial for predicting their behavior in fluids.
- Previous studies have lacked a unified approach to describe their complex geometries.
Purpose of the Study:
- To investigate the hydrodynamic properties of rigid fractal aggregates in shear flow.
- To develop a method for extracting average hydrodynamic characteristics from disordered aggregate structures.
- To explain the relationship between aggregate size, stress, and restructuring.
Main Methods:
- Utilizing Stokesian dynamics to simulate aggregate motion in shear flow.
- Analyzing the total force and torque on aggregates to determine equilibrium values.
- Rescaling particle positions with the geometric radius of gyration to identify universal patterns.
Main Results:
- Average drag-force distributions for fractal aggregates are symmetric and collapse onto a master curve.
- This master curve is characteristic of the aggregate's nature, independent of its specific disordered geometry.
- The study explains power-law behaviors of stress and force moments with aggregate size.
Conclusions:
- The findings provide a universal description of hydrodynamic interactions for rigid fractal aggregates.
- The results explain the scaling of forces and moments with aggregate size.
- Colloidal aggregates, even small ones, are predicted to undergo restructuring under typical shear flow conditions due to cohesive forces.
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