Rheology and dynamics of a deformable object in a microfluidic configuration: A numerical study

A dilute suspension is studied in a confined geometry with a 3D numerical simulation. The suspended element is a non-Brownian elastic dumbbell. The suspension is confined between two walls in a shear flow. The dynamics of the dumbbell as well as the associated rheology are presented. Despite its simplicity, the system exhibits generic microscopic behaviours of real deformable objects such as vesicles, biological cells or capsules like tumbling or vacillating-breathing. It also reproduces macroscopic behaviours like a shear thinning viscosity characteristic of complex fluids rheology. In addition, the model predicts a confinement law where the intrinsic viscosity varies as ∼ c 1/3 for sufficiently strong confinements ( c is the ratio of dumbbell size over the wall-to-wall distance). A transition from a tumbling regime towards a vacillating-breathing one is found. This mode is promoted further by confinement.