We investigate dynamical evolution of gas in barred galaxies using two-dimensional high-resolution hydrodynamic simulations. The gaseous medium is assumed to be infinitesimally-thin, isothermal, unmagnetized, and non-self-gravitating. To study the effects of various galactic environments on the gas evolution, we vary the gas sound speed cs as well as the mass MBH of a super massive black hole (BH) located at the galaxy center. An introduction of the bar potential produces bar substructure including a pair of dust-lane shocks, a nuclear ring, and nuclear spirals. As the sound speed increases, the dust-lane shocks tend to move closer to the bar major axis, resulting in a smaller nuclear ring. The location of a nuclear ring is independent of the BH mass, suggesting that the ring position is not determined by the Lindblad resonances. Coherent nuclear spirals that develop inside a nuclear ring can persist only when either cs is low or MBH is large: they would otherwise be destroyed by the ring material in eccentric orbits. While the mass inflow rate toward the galaxy center in models with low sound speed is quite small because of the presence of a narrow nuclear ring, it becomes larger than 0.01Surf when cs is large, potentially powering active galactic nuclei in Seyfert galaxies.
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