Suspensions of deformable particles in Poiseuille flows at finite inertia

TL;DR

This paper investigates how deformable particles in a pressure-driven flow affect the suspension's viscosity and particle distribution, revealing shear-thinning behavior and the influence of deformability on particle migration.

Contribution

It provides a detailed numerical analysis of the effects of deformability, inertia, and concentration on suspension rheology and particle migration in Poiseuille flows.

Findings

Suspension exhibits shear-thinning behavior.

Deformable particles tend to migrate towards the channel center.

Effective viscosity depends more on capillary number than Reynolds number.

Abstract

We analyze a suspension of deformable particles in a pressure-driven flow. The suspension is composed of neutrally buoyant initially spherical particles and a Newtonian carrier fluid, and the flow is solved by means of direct numerical simulations, using a fully Eulerian method based on a one-continuum formulation. The solid phase is modeled with an incompressible viscous hyperelastic constitutive relation, and the flow is characterized by three main dimensionless parameters, namely the solid volume fraction, the Reynolds and capillary numbers. The dependency of the effective viscosity on these three quantities is investigated to study the inertial effects on a suspension of deformable particles. It can be observed that the suspension has a shear-thinning behavior, and the reduction in effective viscosity for high shear rates is emphasized in denser configurations. The separate analysis of the Reynolds and capillary numbers reveal that the effective viscosity depends more on the capillary than on the Reynolds number. In addition, our simulations exhibit a consistent tendency for deformable particles to move towards the center of the channel, where the shear rate is low. This phenomenon is particularly marked for very dilute suspensions, where a whole region near the wall is empty of particles. Furthermore, when the volume fraction is increased this near-wall region is gradually occupied, because of higher mutual particle interactions. Deformability also plays an important role in the process. Indeed, at high capillary numbers, particles are more sensitive to shear rate variations and can modify their shape more easily to accommodate a greater number of particles in the central region of the channel.