Analytical Solution for Circular Gates as Flow Metering Structures
Publication: Journal of Irrigation and Drainage Engineering
Volume 131, Issue 5
Abstract
Water measurement in irrigation canals is frequently hindered by low head availability and high capital investment costs associated with construction of compatible hydraulic structures. Often irrigation systems have circular sliding gates in place used as diversion and flow control structures. The Fresno Irrigation District investigated the feasibility of using such circular gates (Armco Model 101) as flow metering stations in the 1920s. This early work demonstrated that circular gates could be used simultaneously for both flow control and as flow measurement structures. The original work is compiled by USBR as 10,500 data points and is presented in tabular fashion for gate diameters varying from . An analytical equation of the form , [where is a discharge function which depends on the gate displacement and the nominal gate diameter , represents the gravitational acceleration, and is the hydraulic headloss through the crescent-shaped orifice] accurately predicts most tabulated values. Equations are provided to compute the discharge function for nominal gate diameters varying from for gate displacements between and fully open conditions. The precision of the proposed algorithms are excellent (predicted values are within of the corresponding reported values 95% of the time) for gates greater than .
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References
Hager, W. H. (1987). “Circular gates in circular and U-shaped channels.” J. Irrig. Drain. Eng., 113(3), 413–419.
Hager, W. H., (1994). “Losses in flow.” Wastewater hydraulics. Theory and practice, Springer, Berlin, 77–79.
King, H. W., and Brater, E. F. (1963). “Orifices, gates and tubes.” Handbook of hydraulics for the solution of hydrostatic and fluid-flow problems, 5th Ed., Chap. 4, McGraw-Hill, New York, 4.10–4.10.
United States Department of the Interior. Bureau of Reclamation (USBR). (1953). Irrigation water measurement tables and diagrams. A compilation of data for standard water measurement devices, Washington, D.C., 118–157.
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© 2005 ASCE.
History
Received: Sep 23, 2002
Accepted: Nov 19, 2004
Published online: Oct 1, 2005
Published in print: Oct 2005
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