Simulations of an elastic particle in Newtonian and viscoelastic fluids subjected to confined shear flow

• We study the deformation of elastic particles in fluids under confined shear flow.
• The study is done with a finite element method based code for viscoelastic fluids.
• On the mid plane, the deformed shape of elastic particles is nearly ellipsoidal.
• In Newtonian fluids, out of the mid plane, a particle always migrates to the center.
• In a viscoelastic fluid, the direction of the migration depends on several factors.

The deformation and cross-streamline migration of an initially spherical neo-Hookean elastic particle suspended in confined shear flow of Newtonian and Giesekus viscoelastic fluids is studied through 3D arbitrary Lagrangian Eulerian finite element method numerical simulations. In both a Newtonian and a Giesekus liquid, when suspended in a symmetric position with respect to the walls of the flow cell, the particle deforms until reaching a steady ellipsoid-like shape, with a fixed orientation with respect to the flow direction. The dependences of such deformation and orientation on the flow strength, the geometric confinement, and the rheological properties of the suspending liquid are investigated. If the particle is initially closer to a wall of the channel than to the other, it also migrates transversally to the flow direction. In a Newtonian liquid, migration is always towards the center plane of the channel. In a Giesekus viscoelastic liquid, the migration direction depends on the competition between the elastic and the viscous forces arising in the suspending fluid; in a certain range of constitutive parameters, an ‘equilibrium vertical position’ in between the mid plane and the (upper/lower) wall of the channel is found, which acts as an attractor for particle migration.