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Fragmentation and restructuring of soft-agglomerates under shear.
M L Eggersdorfer1, D Kadau, H J Herrmann
1Particle Technology Laboratory, Institute of Process Engineering, Department of Mechanical and Process Engineering, ETH Zurich, Sonneggstrasse 3, CH-8092 Zürich, Switzerland. meggers@ptl.mavt.ethz.ch
Journal of Colloid and Interface Science
|December 2, 2009
Summary
Soft agglomerates break apart in shear flow, forming smaller fragments with lognormal size distributions. These fragments then relax into more compact structures, following predictable scaling laws.
Area of Science:
- Physics
- Chemistry
- Materials Science
Background:
- Soft agglomerates are ubiquitous in natural and industrial processes.
- Understanding their behavior under flow is crucial for process optimization.
- Previous studies have explored agglomerate dynamics, but a comprehensive DEM analysis of fragmentation and relaxation is lacking.
Purpose of the Study:
- To investigate the restructuring, fragmentation, and relaxation dynamics of soft agglomerates in simple shear flow.
- To elucidate the relationship between shear rate, fragmentation onset, and fragment characteristics.
- To establish scaling laws governing agglomerate behavior.
Main Methods:
- Discrete Element Method (DEM) simulations were employed to model soft agglomerates.
- Agglomerates were subjected to simple shear flow, with van der Waals forces governing inter-particle interactions.
- Fragmentation events and fragment relaxation were tracked over time.
Main Results:
- Agglomerates rotate and elongate in shear flow, fracturing at weakest points into lognormally distributed fragments.
- Fragments relax into more compact structures than the parent agglomerates.
- Generalized scaling laws were derived for fragment mass and size, correlating with shear rate and fragmentation time-lag.
Conclusions:
- The study provides a detailed DEM-based understanding of soft agglomerate fragmentation and relaxation in shear flow.
- The findings are consistent with existing experimental and theoretical literature.
- Initial agglomerate fractal dimension impacts final fragment characteristics, offering insights for material design.
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