- The effect of the bend radius on the gas-solids flow characteristics in pneumatic conveying systems has been investigated numerically. It was evident that the cross-sectional concentration of the particles after a bend is not uniform and that rope regions are formed as the particle-fluid mixture flows through a bend. Predictions of the numerical simulations for different bend radii show that the rope region increases in size as the bend radius is increased. Various cross-sectional concentrations of particles were found for: different pipe to bend radius ratios and particles sizes. It was concluded that the paths taken by the particles after the bend were strongly dependent upon their sizes. This would lead to segregation of the particles in the pipe section following a bend.