The internal velocity structure in the Hyades cluster as seen by Hipparcos is compared with realistic
N-body simulations using the NBODY6 code, which includes binary interaction, stellar evolution and
the Galactic tidal field. The model allows to estimate reliably the accuracy of astrometric radial
velocities in the Hyades as derived by Lindegren et al. (2000) and Madsen et al. (2002) from
Hipparcos data, by applying the same estimation procedure on the simulated data. The simulations
indicate that the current cluster velocity dispersion decreases from 0.35 km/s at the cluster centre to a
minimum of 0.20 km/s at 8 pc radius (2-3 core radii), from where it slightly increases outwards. A
clear negative correlation between dispersion and stellar mass is seen in the central part of the cluster
but is almost absent beyond a radius of 3 pc. It follows that the (internal) standard error of the
astrometric radial velocities relative to the cluster centroid may be as small as 0.2 km/s for a suitable
selection of stars, while a total (external) standard error of 0.6 km/s is found when the uncertainty of
the bulk motion of the cluster is included. Attempts to see structure in the velocity dispersion using
observational data from Hipparcos and Tycho-2 are inconclusive.