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Determination of the Settling Rate of Clay/Cyanobacterial Floccules
Published on: June 11, 2018
Stratification of colloidal aggregation coupled with sedimentation
1Instituto de Ciencias Físicas, Universidad Nacional Autónoma de México, Apartado Postal 48-3, 62251 Cuernavaca, Morelos, Mexico. agus@fis.unam.mx
Physical Review. E, Statistical, Nonlinear, and Soft Matter Physics
|February 7, 2007
Summary
Sedimentation causes colloidal aggregates to stratify, with larger clusters settling. This study simulates this process, revealing that sweeping smaller clusters increases aggregate compactness and can lead to anisotropic structures.
Area of Science:
- Colloidal science
- Soft matter physics
- Materials science
Background:
- Sedimentation in colloidal aggregation leads to system stratification, where larger clusters preferentially settle.
- Previous simulations averaged quantities across depths, limiting detailed analysis of depth-dependent aggregate properties.
Purpose of the Study:
- To investigate colloidal aggregation coupled with sedimentation using particle simulations.
- To analyze cluster properties within a fixed depth layer, enabling comparison with experimental measurements.
- To explore the impact of sedimentation on aggregation rates and cluster morphology.
Main Methods:
- Particle-based computer simulation of colloidal aggregation with sedimentation.
- Focusing analysis on clusters within a defined layer of arbitrary thickness at a fixed depth.
- Comparison of aggregation dynamics and cluster scaling with diffusion-limited cluster aggregation (DLCA).
Main Results:
- Confirmed accelerated aggregation rates compared to DLCA, followed by a slowdown.
- Observed that larger settling clusters sweep smaller ones, increasing their compactness.
- Identified different scaling regimes for cluster width and height, leading to self-similar, anisotropic, or non-self-similar clusters depending on sedimentation strength and depth.
Conclusions:
- Sedimentation significantly alters colloidal aggregation, promoting more compact structures than DLCA.
- The study reveals complex cluster morphologies, including anisotropic and non-self-similar aggregates, challenging traditional fractal dimension definitions.
- The simulation approach allows for direct comparison with experiments involving depth-specific sampling or analysis.
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