  The sedimentation of a spherical particle in an elastoviscoplastic fluid in
proximity of a flat wall is investigated by direct numerical simulations. The
governing equations under inertialess conditions are solved by the finite
element method with an Arbitrary Lagrangian-Eulerian formulation to manage the
particle motion. The fluid is modeled with the Giesekus constitutive equation
modified as proposed by Saramito (2007).
  The sedimentation, migration, and angular velocities are computed as a
function of the particle-wall distance for various Weissenberg and Bingham
numbers. The presence of a yield stress reduces the settling velocity and
reverses the migration direction as compared to the purely viscoelastic case.
The effect of the confining wall on the yielded and unyielded regions around
the particle is investigated. The reversed particle migration phenomenon
observed in the elastoviscoplastic fluid is attributed to the different shear
rate distribution around the particle due to the presence of the yielded
region. The negative wake behind the particle is discussed and related to the
axial component of the viscoelastic stress.
