  We studied the properties of the neutral gas in a sample of 38 local
[U]LIRGs, which mainly covers the less explored LIRG luminosity range. This
study is based on the analysis of the spatially integrated and spatially
resolved spectra of the NaD feature obtained with the VIMOS/VLT-IFS. Analyzing
spatially integrated spectra, we find that the contribution of stars to the
observed NaD-EWs is generally small (<35%), and therefore this feature is
dominated by ISM absorption. After subtracting the stellar contribution, we
find that the pure-ISM integrated spectra generally show blueshifted NaD
profiles, indicating neutral gas outflow velocities V in the range 65-260 km/s.
Excluding galaxies with AGNs, V shows a dependency with the SFR of the type V
\propto SFR^0.15 (in rather good agreement with previous results). The
spatially resolved analysis was performed for 40 galaxies, 22 of which have
neutral gas velocity fields dominated by noncircular motions with signatures of
cone-like winds. However, a modest number of targets (11/40) show disk
rotation. We found that the wind masses are in the range (0.4-7.5)x10^8 Msun,
reaching up to 3% of the dynamical mass of the host. The mass rates are
typically only 0.2-0.4 times the SFR indicating that, the mass loss is too
small to slow down the SF significantly. In the majority of cases, the velocity
of the outflowing gas is not sufficient to escape the host potential well and,
therefore, most of the gas rains back into the disk. On average V/v(esc) is
higher in less massive galaxies, confirming that the galaxy mass has a primary
role in shaping the recycling of gas and metals. The comparison between the
wind power and kinetic power of the starburst associated with SNe indicates
that the starburst could drive the outflows in nearly all the [U]LIRGs
galaxies, as the wind power is generally lower than 20% of the kinetic power
supplied by the starburst.
