  We try to determine the Galactic structure by comparing the observed and
modeled velocities of OB-associations in the 3 kpc solar neighborhood. We made
N-body simulations with a rotating stellar bar. The galactic disk in our model
includes gas and stellar subsystems. The velocities of gas particles averaged
over large time intervals ($\sim 8$ bar rotation periods) are compared with the
observed velocities of the OB-associations. Our models reproduce the directions
of the radial and azimuthal components of the observed residual velocities in
the Perseus and Sagittarius regions and in the Local system. The mean
difference between the model and observed velocities is $\Delta V=3.3$ km
s$^{-1}$. The optimal value of the solar position angle $\theta_b$ providing
the best agreement between the model and observed velocities is
$\theta_b=45\pm5^\circ$, in good accordance with several recent estimates. The
self-gravitating stellar subsystem forms a bar, an outer ring of subclass
$R_1$, and slower spiral modes. Their combined gravitational perturbation leads
to time-dependent morphology in the gas subsystem, which forms outer rings with
elements of the $R_1$- and $R_2$-morphology. The success of N-body simulations
in the Local System is likely due to the gravity of the stellar $R_1$-ring,
which is omitted in models with analytical bars.
