  Using two-dimensional radiation hydrodynamic simulations, we investigate
origin of the ultra fast outflows (UFOs) that are often observed in luminous
active galactic nuclei (AGNs). We found that the radiation force due to the
spectral lines generates strong winds (line-driven disk winds) that are
launched from the inner region of accretion disks (~30 Schwarzschild radii). A
wide range of black hole masses ($M_{\rm BH}$) and Eddington ratios
($\varepsilon$) was investigated to study conditions for causing the
line-driven winds. For $M_{\rm BH} = 10^6-10^9 M_\odot$ and $\varepsilon =
0.1-0.7$, funnel-shaped disk winds appear, in which dense matter is accelerated
outward with an opening angle of 70-80 deg and with 10% of the light speed. If
we observe the wind along its direction, the velocity, the column density, and
the ionization state are consistent with those of the observed UFOs. As long as
the obscuration by the torus does not affect the observations of X-ray bands,
the UFOs could be statistically observed in about 13-28% of the luminous AGNs,
which is not inconsistent with the observed ratio (~40%). We also found that
the results are insensitive to the X-ray luminosity and the density of the disk
surface. Thus, we can conclude that the UFOs could exist in any luminous AGNs,
such as narrow-line Seyfert 1s (NLS1s) and quasars with $\varepsilon > 0.1$, in
which fast line-driven winds are associated.
