Numerical study of saltation of non-uniform grains

Abstract

A theoretical model of non-uniform saltating grains in a turbulent open-channel flow based on the Lagrangian approach is developed. In the analysis described herein, a more realistic stochastic model of particle-bed collision is proposed. Based on geometrical considerations, new formulas for the minimum and maximum values of the angle of the collision surface with an irregular bed are derived. A Monte Carlo simulation of the distribution of saltating and colliding particles is introduced. Numerical simulations of possible particles trajectories with different sizes in an open-channel flow are presented. It is demonstrated that the particle-bed collision mechanism exactly depends on different particles sizes and the bed structure. Application for the analysis of the longitudinal saltating particle diffusion is presented, and the problem with the initial conditions in numerical simulations of particle motion is briefly described.

Keywords:

• Collision angle
• Lagrangian approach
• particle-bed collision
• particle diffusion
• saltation

Acknowledgements

This work was supported by The National Science Centre, Grant No. N N306 658140 “Development of two-layer hydrodynamic model of bed-load sediment transport comprising saltation motion and moving bed”. I am grateful to W. Czernuszenko, Z. Lewandowska, V.I. Nikora, and P.M. Rowiński with whom I have been fortunate to discuss this topic.