  We show that the clogging susceptibility and flow of particles moving through
a random obstacle array can be controlled with a transverse or longitudinal ac
drive. The flow rate can vary over several orders of magnitude, and we find
both an optimal frequency and an optimal amplitude of driving that maximizes
the flow. For dense arrays, at low ac frequencies a heterogeneous creeping
clogged phase appears in which rearrangements between different clogged
configurations occur. At intermediate frequencies a high mobility fluidized
state forms, and at high frequencies the system reenters a heterogeneous frozen
clogged state. These results provide a technique for optimizing flow through
heterogeneous media that could also serve as the basis for a particle
separation method.
