  We explore the dynamics of driven magnetic flux lines in disordered type-II
superconductors in the presence of twin boundaries oriented parallel to the
direction of the applied magnetic field, using a three-dimensional elastic line
model simulated with Langevin molecular dynamics. The lines are driven
perpendicular to the planes to model the effect of an electric current applied
parallel to the planes and perpendicular to the magnetic field. A study of the
long-time non-equilibrium steady states for varying sample orientation and
thickness reveals a rich collection of dynamical regimes spanning the depinning
crossover region that separates the pinned and moving-lattice states of vortex
matter. We observe the emergence of a preferred direction for the ordering of
the Abrikosov lattice in the free-flowing vortex regime due to asymmetric
pinning by the planar defects. We have performed novel direct measurements of
flux line excitations such as half-loops and double kinks to aid the
characterization of the topologically rich flux flow profile.
