Rheology of Colloidal Particles in a Confined Channel under Shear Flow by Brownian Dynamic Simulations

Area of Science:

• Colloid Science
• Soft Matter Physics
• Computational Fluid Dynamics

Background:

• Confined colloidal systems exhibit unique behaviors influenced by particle interactions and boundary conditions.
• Understanding particle dynamics under flow is crucial for applications in materials science and microfluidics.

Purpose of the Study:

• To investigate the concentration profiles and dynamic behavior of charged colloidal particles confined between charged walls under static and shear flow conditions.
• To compare simulation results with theoretical approximations and analyze the impact of wall charge and separation on system properties.

Main Methods:

• Brownian Dynamics (BD) simulations were employed to model the colloidal system.
• Results were compared with Hypernetted Chain Approximation (HNC) and Monte Carlo (MC) simulations for validation.

Main Results:

• BD simulations accurately predicted concentration profiles, agreeing well with HNC and MC results under static conditions.
• Shear flow disrupted equilibrium, leading to structureless systems, reduced transversal particle mobility, and non-Newtonian, shear-thinning viscosity.
• Decreased wall separation and repulsive walls enhanced slip velocity and reduced viscosity, exhibiting power-law behavior.

Conclusions:

• The study highlights the significant influence of confinement, particle concentration, and inter-particle/wall interactions on the rheological properties of colloidal suspensions.
• Shear flow induces significant structural changes and non-Newtonian behavior in confined charged colloidal systems.
• Apparent slip and shear-thinning viscosity are key characteristics observed, with behavior modulated by wall interactions and confinement levels.