We have performed numerical simulations of a monolayer of a bidisperse suspension of colloidal particles in a cylindrical Couette flow taking into account hydrodynamic interactions (HI). We compare our simulation results with a simple phenomenological model and obtain good agreement for the monodisperse case. For a bidisperse suspension, we also obtain a good agreement if the ratio of the radii of the two kind of particles is smaller than 0.5. In a second part, we simulate a two-dimensional bidisperse suspension submitted to a simple shear flow and observe, when HI are disregarded, a local segregation with the formation of stripes along the velocity lines
