  The behaviour of dense assemblies of dry grains submitted to continuous shear
deformation has been the subject of many experiments and discrete particle
simulations. This paper is a collective work carried out among the French
research group GDR Milieux Divis\'es. It proceeds from the collection of
results on steady uniform granular flows obtained by different groups in six
different geometries both in experiments and numerical works. The goal is to
achieve a coherent presentation of the relevant quantities to be measured i.e.
flowing thresholds, kinematic profiles, effective friction, etc. First, a
quantitative comparison between data coming from different experiments in the
same geometry enforces the robust features in each case. Second, a transversal
analysis of the data across the different configurations, allows us to identify
the relevant dimensionless parameters, the different flow regimes and to
propose simple interpretations. The present work, more than a simple
juxtaposition of results, underlines the richness of granular flows and
enhances the open problem of defining a single rheology
