Analysis of particle focusing in a stratified flow using Lattice Boltzmann Simulations

We develop a model which captures the dynamics of a particle, traversing streamlines in a stratified flow using the Lattice Boltzmann Method (LBM). The different hydrodynamic forces acting on the particle, cause it to undergo a cross-stream motion. The introduction of stratified co-flow of two liquids with different viscosities alters the gradient of the velocity profile as compared to a single phase flow. This change affects the shear gradient induced lift force acting on the particle, which enables us to manipulate its final equilibrium position. We analyse how different parameters like viscosity ratio, particle size, particle diameter to channel width ratio and the Reynolds number can affect the final equilibrium position of the particle. Differently sized particles can be made to attain distinct equilibrium positions by tuning these flow parameters. The analysis can be used to develop an efficient particle/cell separator or a microfluidic solution exchanger which has applications in the bio-medical field.

Keyword: Lattice Boltzmann Method, Particle focusing, Stratified flow