Experimental and theoretical study of bed load particle velocity

This paper reports an experimental study of sediment particle velocity in the Hydraulic Engineering Laboratory at the University of Arizona. The experiments were performed in a rectangular channel filled with a layer of coarse sand or gravel. The instantaneous particle velocity was measured by using the images captured with a commercial camera. An innovative image processing technique was developed for tracking individual particle motion, which leads to the determination of instantaneous particle velocity vector. Both the mean particle velocity and the distribution of particle velocities were analyzed. It was found that the instantaneous bed shear stress dominated the particle velocity as well as the probability density function of its distribution. This observation is consistent with the theoretically derived equations for particle velocity and its distribution. Furthermore, the Kolmogorov–Smirnov test confirmed the agreement between the distribution of experimental data and that obtained from the theoretical analysis.