A better understanding of the abrasive waterjet (AWJ) nozzle internal multiphase flow is crucial for improving AWJ machining performance. Simulation of the internal flow and the particle movement in the abrasive entrained waterjet nozzle was conducted based upon the Euler-Lagrange approach and the Discrete Particle Model was used to calculate the abrasive particle trajectories. The particle shape factor and the energy loss due to particle-wall interactions were considered in the numerical model. The results indicate that a longer focus tube can reduce the particle circumferential movement and thus ensure the particles exiting the nozzle without large circumferential velocities. A decrease of particle shape factor will improve the particle acceleration process. The effects of particle density and particle diameter are analyzed. The reported results will provide guidance for AWJ applications and the design of AWJ nozzle. (C) 2016 Elsevier B.V. All rights reserved.