Particle–particle collision in Lagrangian modelling of saltating grains

Abstract

The effect of particle–particle collision on the trajectories of saltating grains in open-channel flows is investigated. The vertical distributions of saltating particles are also analysed. A stochastic particle–particle collision model was designed to determine the collision probability along a particle trajectory, based on the assumption that inter-particle collision frequency may be described by the formula of kinetic gas theory. This parameter is the key quantity for the calculation of collision probability. The Monte Carlo simulation method is used to obtain the velocity and concentration of saltating particles. It is the first attempt to apply a probabilistic inter-particle collision approach to Lagrangian modelling of saltating grains. Trajectories of different particles with and without particle–particle collision are compared with available data. The proposed procedure allows verification of the hypothesis regarding the effect of the particle–particle collision on sediment transport. The described mechanism affects the vertical particle concentration and therefore may play an essential role in bed-load sediment transport.

Keywords:

• Lagrangian model
• particle–particle collision
• saltating particle
• sediment transport
• turbulent velocity field

Acknowledgements

This research was supported by the Polish–British Young Scientists Programme. The author is grateful to W. Czernuszenko, V. Nikora and P. Rowiński for stimulating discussions.