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Restructuring and break-up of two-dimensional aggregates in shear flow
Nikolina D Vassileva1, Dirk van den Ende, Frieder Mugele
1Physics of Complex Fluids, Department of Science and Technology, Institute of Mechanics, Processes and Control-Twente, University of Twente, P.O. Box 217, 7500 AE Enschede, The Netherlands.
Langmuir : the ACS Journal of Surfaces and Colloids
|May 17, 2006
Summary
Glass particle aggregates at water interfaces break apart at a consistent critical shear rate, regardless of size. Their structure changes to a denser, hexagonal form before breaking, as confirmed by a new theoretical model.
Area of Science:
- Fluid dynamics
- Materials science
- Surface science
Background:
- Particle aggregates at fluid interfaces are common in natural and industrial processes.
- Understanding their stability under shear stress is crucial for predicting their behavior.
Purpose of the Study:
- To investigate the critical shear rate for the break-up of 2D glass particle aggregates at a water/air interface.
- To analyze the structural evolution of aggregates before break-up.
- To develop a theoretical model explaining the break-up phenomenon.
Main Methods:
- Experimental investigation of aggregate break-up in simple shear flow.
- Observation of aggregate structural changes using microscopy.
- Development of a theoretical model based on force balance (capillary and drag forces).
Main Results:
- Aggregates of varying sizes exhibited a consistent critical shear rate (1.8 ± 0.2 s⁻¹) for break-up.
- Increasing shear rate led to more circular aggregate shapes and denser, hexagonal particle ordering.
- The theoretical model predicted a weak size dependence of the critical shear rate, aligning with experimental findings.
Conclusions:
- Aggregate break-up at the water/air interface is largely independent of aggregate size.
- Structural ordering and shape change precede aggregate disintegration under shear flow.
- The developed model provides a valid framework for understanding interfacial aggregate stability.