On three-dimensional continuous saltating process of sediment particles near the channel bed

Abstract

The purpose of this study is to develop a three-dimensional continuous saltation model which is able to simulate the saltating behaviors of a single particle near the channel bed. A real-time flow visualization system, including two charge-coupled device cameras, an image-grabbing card and an OPTIMAS image-processing software, is developed to measure the three-dimensional saltating trajectories and corresponding velocity components. The averaged dimensionless saltation length, height and width were found to follow Pearson type III distributions and the dimensionless saltation velocity follows a normal distribution. The impacting and rebounding angles increase as the flowtransport capacity T_* increases. The rebounding angles, under various impacting conditions, follow a normal distribution. Based on the data colleted, an impacting and rebounding mechanism is derived, and thus a three-dimensional saltation model is established to simulate the dynamic characteristics of the saltating particles. Regression equations for the important saltating characteristics, including saltation length, height, width and three-dimensional velocity components were obtained. Based on these equations, bed load equation was derived. This equation tends to slightly overestimate the bed load transport. Nevertheless, the overall accuracy is satisfactory.