Flow characteristics of pneumatic conveying of stiff shotcrete based on CFD-DEM method

Simulation of Two-Phase Flow of Shotcrete in a Bent Pipe Based on a CFD–DEM Coupling Model

To solve the problems in determining the interactions among particles and between particles and pipe walls in pneumatic conveying systems in field tests, this article studied the two-phase flow motion characteristics of shotcrete in pipes based on a CFD–DEM coupling model and field measurement. The movement of the shotcrete, which is affected by the gas phase in the pipe, was simulated for different bend angles, and the velocity of the shotcrete material and pressure distribution within the pipeline were determined. The simulation results show that at the ideal wind pressure, the inelastic collisions among the particles and between the particles and pipe wall cause the accumulation of shotcrete material in the outside area of the bent pipe section, which may block the pipe; nevertheless, the blockage is prevented by the turbulent and secondary flows, which disperse the particles to different degrees. In addition, the wear amounts caused by particles in pipes with different bend angles were quantified. With increasing bend angle, the wear points gradually diffuse radially toward the outside wall of the bent pipe. Additionally, the wear loss decreases and then increases with increasing bend angle. The particle velocity exhibits the minimal loss at a bend angle of 90°. It was concluded that the energy loss of the aggregate particles in the elbow of the pipe is approximately 30 times that in a horizontal, straight pipe. The results of this study can provide guidance in the construction field and for numerical simulations of the pneumatic conveying process of shotcrete.