We study the behavior of vortex matter in artificial flow channels confined
by pinned vortices in the channel edges (CE's). The critical current Js is
governed by the interaction with static vortices in the CE's. We study
structural changes associated with (in)commensurability between the channel
width w and the natural row spacing b0, and their effect on Js. The
behavior depends crucially on the presence of disorder in the CE arrays. For
ordered CE's, maxima in Js occur at matching w=nb0 (n integer), while
for w=nb0 defects along the CE's cause a vanishing Js. For weak CE
disorder, the sharp peaks in Js at w=nb0 become smeared via nucleation
and pinning of defects. The corresponding quasi-1D n row configurations can
be described by a (disordered)sine-Gordon model. For larger disorder and
w≃nb0, Js levels at ∼30 of the ideal lattice strength
Js0. Around 'half filling' (w/b0≃n±1/2), disorder causes new
features, namely {\it misaligned} defects and coexistence of n and n±1
rows in the channel. This causes a {\it maximum} in Js around mismatch,
while Js smoothly decreases towards matching due to annealing of the
misaligned regions. We study the evolution of static and dynamic structures on
changing w/b0, the relation between modulations of Js and transverse
fluctuations and dynamic ordering of the arrays. The numerical results at
strong disorder show good qualitative agreement with recent mode-locking
experiments.Comment: 29 pages, 32 figure