Discontinuous shear thickening in Brownian suspensions by dynamic simulation

Area of Science:

• Soft Matter Physics
• Computational Fluid Dynamics
• Materials Science

Background:

• Shear thickening is a complex rheological behavior observed in dense suspensions.
• Previous models often struggle to quantitatively capture experimental observations in colloidal systems.
• Understanding the transition from lubricated to frictional contact is key to explaining this phenomenon.

Purpose of the Study:

• To investigate the fundamental mechanisms of shear thickening in dense colloidal suspensions.
• To determine the relative contributions of hydrodynamic, frictional, Brownian, and repulsive forces.
• To achieve quantitative agreement with experimental data for viscosity and normal stress differences.

Main Methods:

• Particle-scale numerical simulations of dense colloidal suspensions.
• Modeling of lubricated, frictionally contacting, Brownian, and short-range repulsive forces.
• Analysis of stress-induced transitions and jamming volume fraction sensitivity.

Main Results:

• Shear thickening is a geometric phenomenon driven by the transition to frictional contacts.
• Brownian and repulsive forces additively influence the onset stress of shear thickening.
• Simulations incorporating Brownian and stabilizing forces show excellent agreement with experimental viscosity (η) and second normal stress difference (N2).

Conclusions:

• The nature of contact forces, particularly friction, is crucial for shear thickening in suspensions.
• Short-range repulsive potentials are essential for quantitative agreement with experimental rheological data.
• Dynamic particle simulations provide a powerful tool for understanding complex suspension behavior.