Mesoscopic model for soft flowing systems with tunable viscosity ratio

TL;DR

This paper introduces a mesoscopic lattice Boltzmann model for binary fluid mixtures with adjustable viscosity ratios, enabling better simulation of soft flowing systems and microfluidic applications.

Contribution

It develops a two-range pseudo-potential lattice Boltzmann method with tunable viscosity ratio and positive disjoining pressure, extending simulation capabilities for soft flows.

Findings

Achieves a wider range of surface tension values.

Ensures positive disjoining pressure regardless of viscosity ratio.

Successfully simulates effective viscosity of emulsions in channels.

Abstract

We propose a mesoscopic model of binary fluid mixtures with tunable viscosity ratio based on a two-range pseudo-potential lattice Boltzmann method, for the simulation of soft flowing systems. In addition to the short range repulsive interaction between species in the classical single-range model, a competing mechanism between the short-range attractive and mid-range repulsive interactions is imposed within each species. Besides extending the range of attainable surface tension as compared with the single-range model, the proposed scheme is also shown to achieve a positive disjoining pressure, independently of the viscosity ratio. The latter property is crucial for many microfluidic applications involving a collection of disperse droplets with a different viscosity from the continuum phase. As a preliminary application, the relative effective viscosity of a pressure-driven emulsion in a planar channel is computed.