A numerical simulation of the disk dynamics of a flat stellar-gaseous
galaxy is presented. This simulation is based on N-body modelling for
a stellar disk, together with integration of the two-dimensional hydro
dynamic equations for a gaseous disk. The existence of a quasi-periodi
c regime of disk evolution found earlier in a purely hydrodynamic simu
lation is confirmed. intense gas hows in the central area of the disk
due to the saddle point of the bar potential can support the active ga
lactic nuclei in Seyfert galaxies and form double nuclei.