Computing the Trajectory of Free Jets
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VIEW THE REPLYPublication: Journal of Hydraulic Engineering
Volume 134, Issue 2
Abstract
In recent years, design floods have increased beyond spillway capacity at numerous large dams. When additional spillway capacity is difficult or expensive to develop, designers may consider allowing the overtopping of a dam during extreme events. For concrete arch dams, this often raises issues of potential erosion and scour downstream from the dam, where the free jet initiating at the dam crest impacts the abutments and the downstream river channel. A recent review has shown that a commonly cited equation for predicting the trajectory of free jets is flawed, producing jet trajectories that are much too flat in this application. This could lead analysts to underestimate the amount of scour that could occur near a dam foundation, or conversely to overestimate the extent of scour protection required. This technical note presents the correct and incorrect jet trajectory equations, quantifies the errors associated with the flawed equation, and summarizes practical information needed to model the trajectory of free jets overtopping dam crests.
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References
Annandale, G. W. (2006). Scour technology: Mechanics and engineering practice, McGraw-Hill, New York, 146–151.
Bureau of Reclamation. (1960). Design of small dams, 1st Ed., United States Department of the Interior, United States Government Printing Office, Denver, 282–291.
Bureau of Reclamation. (1976). Design of gravity dams, United States Department of the Interior, United States Government Printing Office, Denver, 198–199.
Bureau of Reclamation. (1977). Design of arch dams, United States Department of the Interior, United States Government Printing Office, Denver, 312–313.
Bureau of Reclamation. (1987). Design of small dams, 3rd Ed., United States Department of the Interior, United States Government Printing Office, Denver, 365–387.
Chow, V. T. (1959). Open-channel hydraulics, McGraw-Hill, New York, 360–361.
Davis, A. C., Ellett, B. G. S., and Jacob, R. P. (1998). “Flow measurement in sloping channels with rectangular free overfall.” J. Hydraul. Eng., 124(7), 760–763.
Davis, A. C., Jacob, R. P., and Ellett, B. G. S. (1999). “Estimating trajectory of free overfall nappe.” J. Hydraul. Eng., 125(1), 79–82.
Delleur, J. W., Dooge, J. C. I., and Gent, K. W. (1956). “Influence of slope and roughness on the free overfall.” Proc. American Society of Civil Engineers, Vol. 82, No. HY4 Paper No. 1038, 1038-30–1038-35.
Halliday, D., and Resnick, R. (1981). Fundamentals of physics, 2nd Ed., Wiley, New York, 44–46.
Henderson, F. M. (1966). Open channel flow, MacMillan, New York, 191–197.
Peterka, A. J. (1958). Hydraulic design of stilling basins and energy dissipators, Engineering Monograph No. 25, U.S. Dept. of the Interior, Bureau of Reclamation, Denver, 201–203.
Rajaratnam, N., Muralidhar, D., and Beltaos, S. (1976). “Roughness effects on rectangular free overfall.” J. Hydr. Div., 102(HY5), 599–614.
Rouse, H. (1936). “Discharge characteristics of the free overfall.” Civ. Eng. (N.Y.), 6, 257.
Rouse, H. (1943). “Discussion of energy loss at the base of a free overfall.” Trans. Am. Soc. Civ. Eng., 108, 1383–1387.
U.S. Army Corps of Engineers. (1964). “High overflow dams, energy dissipators, flip bucket throw distance.” Hydraulic design criteria, sheet 112-8, Coastal and Hydraulics Laboratory, Engineer Research and Development Center, Waterways Experiment Station, Vicksburg, Miss.
U.S. Army Corps of Engineers. (1987). “Overflow spillway crest.” Hydraulic design criteria, sheets 111-1 to 111-2/1, Coastal and Hydraulics Laboratory, Engineer Research and Development Center, Waterways Experiment Station, Vicksburg, Miss.
Wahl, T. L. (2001). “Hydraulic performance of Coanda-effect screens.” J. Hydraul. Eng., 127(6), 480–488.
Information & Authors
Information
Published In
Journal of Hydraulic Engineering
Volume 134 • Issue 2 • February 2008
Pages: 256 - 260
Copyright
© 2008 ASCE.
History
Received: May 5, 2006
Accepted: Apr 30, 2007
Published online: Feb 1, 2008
Published in print: Feb 2008
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