Aggregation and Breakup of Particles in a Shear Flow

Area of Science:

• Fluid dynamics
• Particle science
• Rheology

Background:

• Particle aggregation and breakup are critical phenomena in various industrial processes.
• Understanding these dynamics in different flow conditions is essential for process optimization.

Purpose of the Study:

• To experimentally investigate particle aggregation and breakup in a Couette flow system.
• To identify different flow regimes based on shear stress and particle concentration.
• To determine the factors influencing aggregate size in each regime.

Main Methods:

• Experiments were conducted using monodisperse and polydisperse particle suspensions.
• Varying particle volume concentrations and constant inner cylinder rotation speed in a Couette flow setup.
• Analysis of aggregate size distribution under different shear stress conditions.

Main Results:

• Three distinct aggregation regimes were observed, dependent on shear stress and particle concentration.
• At low concentrations, aggregate size depended solely on shear stress.
• At higher concentrations, aggregate size was influenced by both shear stress and concentration, with a transition from laminar to turbulent flow.
• In turbulent flow, aggregate size was governed by the Kolmogorov length scale, independent of primary particle size.
• In laminar flow, aggregate size showed a slight inverse relationship with primary particle diameter.

Conclusions:

• The study elucidates the complex interplay between flow hydrodynamics and particle concentration in dictating aggregate morphology.
• The findings highlight the critical role of flow regime (laminar vs. turbulent) in particle aggregation dynamics.
• The results provide valuable insights for controlling particle aggregation in industrial applications involving shear flows.