From local to hydrodynamic friction in Brownian motion: A multiparticle collision dynamics simulation study.

Area of Science:

• Colloid science
• Fluid dynamics
• Computational physics

Background:

• Understanding colloidal particle behavior in fluids is crucial for materials science.
• Hydrodynamic interactions govern particle motion and diffusion.
• Existing models often assume no-slip conditions or additive diffusion.

Purpose of the Study:

• To determine friction and diffusion coefficients for spherical colloids.
• To investigate the effects of slip vs. no-slip boundary conditions.
• To explore fluid models with and without angular momentum conservation.

Main Methods:

• Mesoscale hydrodynamic simulations using multiparticle collision dynamics.
• Analysis of velocity and force autocorrelation functions.
• Integration of numerical and theoretical hydrodynamic expressions for diffusion.

Main Results:

• No-slip conditions yield Stokes' law.
• Slip conditions reduce hydrodynamic friction, deviating from classical results.
• Diffusion coefficients show minor deviations from Stokes-Einstein relation, disappearing for larger colloids.

Conclusions:

• Hydrodynamic friction is reduced for slip boundary conditions.
• The additivity of local and hydrodynamic diffusion coefficients is contradicted for slip conditions.
• Simulation results validate the approach for predicting colloid behavior.