  With a help of hydrodynamical models, we explore fundamental modes of gas
flow in central parts of a galaxy potential with non-axisymmetric perturbations
of various strengths. Our grid-based algorithm allows us to get a detailed
picture of gas dynamics down to about 10 pc from the galaxy center, where the
central black hole becomes dominant. Gas inflow in a bar with an Inner Lindblad
Resonance often stops at the nuclear ring. We find that embedded bars in
resonant coupling are unlikely to increase the inflow, but for certain gas
parameters in a single bar, inflow to the center develops in a spiral shock,
similar to the patterns observed in nuclear discs of real galaxies. The spiral
pattern persists for very weak non-axisymmetries of the potential.
