  For the nearby dwarf star alpha Cen B (K1 V), we present limb darkening
predictions from a 3D hydro-dynamical radiative transfer model of its
atmosphere. We first compare the results of this model to a standard Kurucz's
atmosphere. Then we use both predictions to fit the new interferometric
visibility measurements of alpha Cen B obtained with the VINCI instrument of
the VLT Interferometer. Part of these new visibility measurements were obtained
in the second lobe of the visibility function, that is sensitive to stellar
limb darkening. The best agreement is found for the 3D atmosphere limb
darkening model and a limb darkened angular diameter of theta\_3D =
6.000+-0.021 mas, corresponding to a linear radius of 0.863+-0:003Ro (assuming
pi = 747.1+-1.2 mas). Ournew linear radius is in good agreement with the
asteroseismic value predicted by Thevenin et al. (2002). In view of future
observations of this star with the VLTI/AMBER instrument, we also present limb
darkening predictions in the J, H and K bands.
