Numerical simulations on the dynamics of a particle pair in a viscoelastic fluid in a microchannel: effect of rheology, particle shape, and confinement

The dynamics of two particles suspended in a viscoelastic fluid and aligned on the centerline of a microfluidic channel is investigated by direct numerical simulations. The shear-thinning elastic fluid is modeled by the Giesekus constitutive equation. The relative particle velocity is studied by varying the interparticle distance, the Deborah number, fluid shear thinning, confinement ratio, and particle shape. Concerning the latter aspect, spherical and spheroidal particles with different aspect ratios are considered. The regimes of particle attraction and repulsion as well as the equilibrium configurations are identified and correlated with the fluid rheological properties and particle shape. The observed dynamics is related to the distribution of the viscoelastic normal stresses in the fluid between the particles. The results reported here provide useful insights into design efficient microfluidics devices to achieve particle ordering, i.e., the formation of equally spaced particle structures.