Experimental Investigation of Saltation Characteristics of Particles near Channel Bed

Document Type : Research Paper

Authors

1 Ph.D Student of Water Eng., Khajeh Nasir Toosi University of Tech., Tehran

2 Prof. of Hydraulic Structures, Dept. of Civil Eng., Tarbiat Modarres University, Tehran

Abstract

This paper studies the mechanical characteristics of saltation of bed-load particles in turbulent flows. Experiments have been carried out by means of high speed photography to obtain saltation characteristics such as length, height, velocity, impacting and rebounding angles for different hydraulic conditions, particle size, density and bed roughness by analyzing and processing pictures taken at 250 frames per second. The measured values of the parameters showed that increases in turbulence parameters of the flow increase saltation length, height, and velocity but decrease the impacting and rebounding angles. It was also found that saltation length and height tended to increase as the average size of the bed material (d50) increased. To solve numerical trajectory equations, the initial velocity component of the particle must be known. The initial longitudinal particle velocity was found to range from 3u* to 8u* and its vertical velocity ranged from 1.5u* to 3.5u*, which were different from the values reported in the literature. The longitudinal and vertical components of the restitution coefficient were also measured and it was seen that the Shields parameter (t*) had no meaningful effect on these components, remaining almost constant with increasing.

Keywords

References

1- Hu, Ch., and Hui, Y. (1996). “Bed-load transport. I: Mechanical characteristics.” J. Hydraulic Eng., 122(5), 245-254.
2- Van Rijn, C. L. (1984). “Sediment transport,part 1: Bed load transport. ” J. Hydraulic Eng., 110(10),
1431-1456.
3- Van Rijn, L. (1993). Principles of sediment transport in rivers, estuaries and coastal seas, 1st Ed., Aqua Pub., Netherlands.
4- Sekine, M., and Kikkawa, H. (1992). “Mechanics of saltating grains. II.” J. Hydraulic Eng., 118(4), 536-558.
5- Lee, H., and Hsu, I.(1994). “Investigation of saltating particle motions. ” J. Hydraulic Eng., 120(7), 831-845.
6- Nino, Y., and Garcia, M. (1998). “Experiments on saltation of sand in water.” J. Hydraulic Eng., 124(10), 1014-1025.
7- Nino, Y., and Garcia, M. (1998). “Using lagrangian particle saltation observations for bedload sediment transport modeling.” Hydrological Processes, 12, 1197-1218.
8- Ancey, Ch., and Bigillon, F., Frey, P.H., and Ductet, R. (2002). “Saltation motion of a bead in a rapid water stream.” Physical Review E, 66 (3), 1-16.
9- Lee, H., Chen, Y. H., You, J. Y., and Lin, Y. T. (2000). “Investigation of continuous bed load saltating process.” J. Hydraulic Eng., 126(9), 691-700.
10- Lee, H., Lin, Y. T., You, J. Y., and Wang, H. W. (2006). “On three-dimensional continuous saltating process of sediment particles near the channel bed. ” J. Hydraulic Research, 44(3), 374-389.
11- Lee, H., You, J. Y., and Lin, Y. T. (2002). “Continuous saltating process of multiple sediment particles.” J. Hydraulic Eng., 128(4), 443-450.
12- Ling, Ch.(1995). “Criteria for incipient motion of spherical sediment particles” J. Hydraulic Eng., 121(6), 472-478.
Journal of Water and Wastewater; Ab va Fazilab ( in persian )
Volume 22, Issue 1 - Serial Number 1
Serial number:77
March 2011
Pages 92-100

Files

Share

How to cite

Statistics