Particle trajectories in pipe flow considering particle-wall collisions

Particle-wall collision behaviors have strong effects on confined particle-laden pipe flows, which are important in pneumatic conveying and pulverized coal combustion. In this paper, a numerical simulation of a pipe flow was conducted to analyze the effects of different initial conditions and particle-wall collision model parameters. The results show that a realistic collision model with coefficients provided by experiments can predict accurate particle exit velocity distributions. The effects of the initial motion of the particles diminish at the exit as long as the pipe length and the number of wall collisions are sufficient, and larger particles require the length to be longer. A simplified collision model with an arbitrary constant restitution coefficient e and a friction coefficient f leads to inaccurate results of the particle exit velocity probability density function, and using constant coefficients from data of a single collision angle will make the model ineffective. It is better to apply a normal distribution for e and a constant f if available collision data are limited, which gets reasonably accurate statistical results despite small distribution deviations.