  When suspended particles are pushed by liquid flow through a constricted
channel they might either pass the bottleneck without trouble or encounter a
permanent clog that will stop them forever. However, they may also flow
intermittently with great sensitivity to the neck-to-particle size ratio D/d.
In this work, we experimentally explore the limits of the intermittent regime
for a dense suspension through a single bottleneck as a function of this
parameter. To this end, we make use of high time- and space-resolution
experiments to obtain the distributions of arrest times T between successive
bursts, which display power-law tails with characteristic exponents. These
exponents compare well with the ones found for as disparate situations as the
evacuation of pedestrians from a room, the entry of a flock of sheep into a
shed or the discharge of particles from a silo. Nevertheless, the intrinsic
properties of our system i.e. channel geometry, driving and interaction forces,
particle size distribution seem to introduce a sharp transition from a clogged
state to a continuous flow, where clogs do not develop at all. This contrasts
with the results obtained in other systems where intermittent flow, with
power-law exponents above two, were obtained.
