Air Entrainment by Spillway Aerators
Publication: Journal of Hydraulic Engineering
Volume 116, Issue 6
Abstract
Aerators on spillways may be regarded as an effective protection against cavitational erosion. The air entrainment of aerators is governed by a number of independent parameters, that include the slopes of the spillway and the aerator, the heights of ramp and offset, the approaching flow depth and Froude number, and the stagnation pressure in the nappe cavity. Based on model observations, two approaches are presented for the air entrainment coefficient β. The first, direct approach is based on the analysis of each effect on β. An expression is presented that should be tested for other geometries. The second, indirect approach is based on the length of jet for zero cavity subpressure. The resulting expression for the maximum air entrainment coefficient may then be corrected for the effect of cavity subpressure. The present approach introduces developing and developed aerator flow conditions. Further, the cavity subpressure is accounted for by a difference Euler number. The final system of equations for β is compared to model and prototype data, and a fair agreement is noted.
Get full access to this article
View all available purchase options and get full access to this article.
References
1.
Chanson, H. (1988). “A model study of aerator performance,” thesis presented to the University of Canterbury, at Christchurch, New Zealand, in partial fulfillment of the requirements for the degree of Doctor of Philosophy.
2.
Falvey, H. T., and Ervine, D. A. (1988). “Aeration in jets and high velocity flows.” Int. Symp. on Model‐Prototype Correlation of Hydr. Structures, P. H. Burgi, ed., ASCE, 25–55.
3.
Hager, W. H. (1983). “Hydraulics of plane free overfall.” J. Hydr. Engrg., 109, 1683–1697.
4.
Koschitzky, H.‐P. (1987). “Dimensionierungskonzept für Sohlbelüfter in Schussrinnen zur Vermeidung von Kavitationsschäden.” Mitteilung 65, Inst., für Wasserbau, Universität Stuttgart, West Germany (in German).
5.
Koschitzky, H.‐P., and Kobus, H. (1988). “Hydraulics and design of spillway aerators for cavitation prevention in high speed flows.” Int. Symp. on Hydr. for High Dams, IAHR, 724–733.
6.
Low, H. S. (1986). “Model studies of Clyde Dam spillway aerators.” Research Report 85‐6, Dept. of Civ. Engrg., Univ. of Canterbury, Christchurch, New Zealand.
7.
Marcano, A., and Castillejo, N. (1984). “Model‐prototype comparison of aeration devices of Guri Spillway.” Symp. on Scale Effects, H. Kobus, ed., IAHR, (4.6), 1–5.
8.
Pan, S., Shao, Y., Shi, Q., and Dong, X. (1980). “The self‐aeration capacity of the water jet over the aeration ramp.” J. Hydr. Engrg. (Shuili Xuebao), Beijing, PRC, 5, Oct., 13‐22 (in Chinese with English abstract).
9.
Pan, S., and Shao, Y. (1984). “Scale effects in modelling air demand by a ramp slot.” Symp. on Scale Effects, H. Kobus, ed., IAHR, (4.7), 1–5.
10.
Pinto, N. L. de S., Neidert, S. H., and Ota, J. J. (1982). “Aeration at high velocity flows.” Water Power and Dam Constr., 34, Feb./Mar., 34–38, 42–44.
11.
Pinto, N. L. de S., Neidert, S. H. (1983). “Evaluating entrained air flow through aerators.” Water Power and Dam Constr., 35, Aug., 40–42.
12.
Rutschmann, P., Volkart, P., and Wood, I. R. (1986). “Air entrainment at spillway aerators.” 9th Australasian Fluid Mech. Conf., ASCE, Auckland, New Zealand, 350–353.
13.
Rutschmann, P. (1987). “Die transversale Druckverteilung unter Sprungstrahlen von Schrussrinnenbelüftern—Folgen für den Lufteintrag.” Wasserwirtschaft, 77(5), 219–223 (in German).
14.
Rutschmann, P. (1988a). “Calculation and optimum shape of spillway chute aerators.” Int. Symp. on Model‐Prototype Correlation of Hydr. Structures, P. H. Burgi, ed., ASCE, Aug., 118–127.
15.
Rutschmann, P. (1988b). “Belüftungseinbauten in Schussrinnen.” Mitteilung Versuchsanstalt für Wasserbau, Hydrologie und Glaziologie, D. Vischer, ed., Zürich, Switzerland (in German).
16.
Schwartz, I., and Nutt, L. P. (1963). “Projected nappes subject to transverse pressure.” J. Hydr. Div., ASCE, 89(7), 97–104.
17.
Tan, P. (1984). “Model studies of aerators on spillways.” Research Report 84‐6, Dept. Civ. Engrg., Univ. of Canterbury, Christchurch, New Zealand.
18.
Volkart, P., and Rutschmann, P. (1984). “Rapid flow in spillway chutes with and without deflectors—A model‐prototype comparison.” Symp. on Scale Effects, H. Kobus, ed., IAHR, (4.5), 1–8.
19.
Wood, I. R. (1984). “Air entrainment in high speed flows.” Symp. on Scale Effects, H. Kobus, ed., IAHR, (4.1), 1–7.
20.
Wood, I. R. (1988). “Aerators—The interaction of nappe and duct air entrainment.” Int. Symp. on Hydr. for High Dams, IAHR, 611–618.
Information & Authors
Information
Published In
Copyright
Copyright © 1990 ASCE.
History
Published online: Jun 1, 1990
Published in print: Jun 1990
Authors
Metrics & Citations
Metrics
Citations
Download citation
If you have the appropriate software installed, you can download article citation data to the citation manager of your choice. Simply select your manager software from the list below and click Download.