  Confined flows of particles can lead to clogging, and therefore failure, of
various fluidic systems across many applications. As a result, design
guidelines need to be developed to ensure that clogging is prevented or at
least delayed. In this Letter, we investigate the influence of the angle of
reduction in the cross-section of the channel on the bridging of semi-dilute
and dense non-Brownian suspensions of spherical particles. We observe a
decrease of the clogging probability with the reduction of the constriction
angle. This effect is more pronounced for dense suspensions close to the
maximum packing fraction where particles are in contact in contrast to
semi-dilute suspensions. We rationalize this difference in terms of arch
selection. We describe the role of the constriction angle and the flow profile,
providing insights into the distinct behavior of semi-dilute and dense
suspensions.
