A lattice Boltzmann study of particle settling in a fluctuating multicomponent fluid under confinement

TL;DR

This study uses advanced lattice Boltzmann simulations to analyze how confinement and thermal fluctuations influence the settling behavior of particles in multicomponent fluids, revealing significant fluctuation enhancements.

Contribution

It introduces a coupled fluctuating lattice Boltzmann and finite-size particle model to investigate particle dynamics under confinement with thermal fluctuations.

Findings

Confinement significantly amplifies velocity fluctuations.

Fluctuations can be an order of magnitude larger than in unconfined systems.

The methodology accurately captures confinement effects on particle motion.

Abstract

We present mesoscale numerical simulations based on the coupling of the fluctuating lattice Boltzmann method (FLBM) for multicomponent systems with a wetted finite-size particle model. This newly coupled methodologies are used to study the motion of a spherical particle driven by a constant body force in a confined channel with a fixed square cross-section. The channel is filled with a mixture of two liquids under the effect of thermal fluctuations. After some validations steps in absence of fluctuations, we study the fluctuations in the particle's velocity at changing thermal energy, applied force, particle size, and particle wettability. The importance of fluctuations with respect to the mean settling velocity is quantitatively assessed, especially in comparison to unconfined situations. Results show that the expected effects of confinement are very well captured by the numerical simulations, wherein the confinement strongly enhances the importance of velocity fluctuations, which can be one order of magnitude larger than what expected in unconfined domains. The observed findings underscore the versatility of the proposed methodology in highlighting the effects of confinement on the motion of particles in presence of thermal fluctuations.