  In this paper, we developed a mathematical model for the sedimentation
process of small particles in a lid-driven cavity flow with an obstacle to
model the transport of microplastic particles in rivers. A stationary
incompressible Navier-Stokes simulation at moderate Reynolds-numbers provides
the background flow field. Spherical particles are injected into this flow
field and their equation of motion is solved to determine the number of
particles that sediment on the surface of the obstacle. To capture the effect
of typical biological organisms and biofilms on the bottom surface of river
beds, the obstacle can exert an attraction force onto the particles. Various
simulations and parameter studies are carried out to determine the influence of
the obstacle geometry, particle densities, and the attraction force on the
sedimentation process.
