  We study the dynamics of galaxy mergers, with emphasis on the gas feeding of
nuclear regions, using a suite of hydrodynamical simulations of galaxy
encounters. The high spatial and temporal resolution of the simulations allows
us to not only recover the standard picture of tidal-torque induced inflows,
but also to detail another, important feeding path produced by ram pressure.
The induced shocks effectively decouple the dynamics of the gas from that of
the stars, greatly enhancing the loss of gas angular momentum and leading to
increased central inflows. The ram-pressure shocks also cause, in many cases,
the entire galactic gas disc of the smaller galaxy to abruptly change its
direction of rotation, causing a complete "flip" and, several $10^8$ yr later,
a subsequent "counter-flip". This phenomenon results in the existence of
long-lived decoupled gas-stellar and stellar-stellar discs, which could hint at
a new explanation for the origin of some of the observed kinematically
decoupled cores/counter-rotating discs. Lastly, we speculate, in the case of
non-coplanar mergers, on the possible existence of a new class of remnant
systems similar to some of the observed X-shaped radio galaxies.
