Lattice Boltzmann - Langevin simulations of binary mixtures

TL;DR

This paper introduces a hybrid numerical method combining lattice Boltzmann and stochastic line methods to simulate fluctuating hydrodynamics in binary mixtures, accurately capturing thermal fluctuations and interface dynamics.

Contribution

It presents a novel hybrid approach that maintains fluctuation-dissipation balance and demonstrates its effectiveness through benchmarking and invariance tests.

Findings

Excellent agreement with analytical correlations

Successful capture of thermally induced capillary fluctuations

Model maintains Galilean invariance

Abstract

We report a hybrid numerical method for the solution of the model H fluctuating hydrodynamic equations for binary mixtures. The momentum conservation equations with Landau-Lifshitz stresses are solved using the fluctuating lattice Boltzmann equation while the order parameter conservation equation with Langevin fluxes are solved using the stochastic method of lines. Two methods, based on finite difference and finite volume, are proposed for spatial discretisation of the order parameter equation. Special care is taken to ensure that the fluctuation-dissipation theorem is maintained at the lattice level in both cases. The methods are benchmarked by comparing static and dynamic correlations and excellent agreement is found between analytical and numerical results. The Galilean invariance of the model is tested and found to be satisfactory. Thermally induced capillary fluctuations of the interface are captured accurately, indicating that the model can be used to study nonlinear fluctuations.