Abstract
We phrase and solve boundary-value problems for the segregation of spheres with either equal density and different sizes, or the same size and different densities in flows of a clear fluid driven by gravity over an inclined, erodible bed in a wide channel. We assume that the flow is steady and uniform, collisions between particles dissipate little energy, and the sizes and masses of the particles are not too different. For particles of the same material with diameters that differ by as little as ten per cent, we find that the flow features, such as velocity, granular temperature and solid concentration profiles, are significantly dif- ferent from those for a flow of a single species with a diameter equal to the average of the two diameters. In particular, the total particle flux of the mixture is significantly larger.