- In hydraulic conveying of solid particles, the flow characteristics play a significant rule on choosing the optimal operating conditions for a desired conveying rate. The main goal of this study is to investigate the flow characteristics in terms of essential operating conditions. For this target 3D CFD-DEM simulations were held to provide information on the hydraulic conveying of coarse particles in a fully developed horizontal flow in a pipe. The simulation was done in a periodic pipeline which was validated with experimental data and showed good agreements for the pressure and concentration profile. Therefore, the modeling and the simulation setup, which are given in this study, can be used as a basis for further investigating this phenomenon. To examine the effects of the operating conditions on the flow, a parametric study was done using NaCl particles and brine as the carrier. This investigation included running several simulations and changing the operating conditions: mean fluid velocity, particle concentration, particle size and pipe size. The results were analyzed to retrieve the pressure drop, the velocity profiles of the phases, the concentration profiles, the turbulent intensity, the delivered concentration and the dominant forces. By analyzing these results, we found how the flow pattern is governed by the operating conditions. In particular, an interesting aspect that found is that in the mean velocity range of 0.6–4 m/s two regimes dominated the flow, below (moving bed) and above the velocity of 1.5 m/s (heterogeneous flow). Furthermore, it is found that the inter-particle collisions are the most dominant effect that support the suspended particles above the bed, which suggest that flow eddies have less significance in that manner.