Experimental Study of the Flow Field over Bottom Intake Racks
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Volume 134, Issue 1
Abstract
Bottom racks made by longitudinal bars are hydraulic structures widely adopted for engineering purposes. In the present paper we revisit the problem of their hydraulic design, analyzing the data obtained from a systematic series of experiments carried out in a laboratory flume. For each run we measured the diverted discharge, the water surface longitudinal profile, and using a two-dimensional backscatter laser Doppler anemometer, we measured the velocity field over the rack and in the slit between two adjacent bars. The latter measurements, in particular, allow us to obtain the along-rack distributions of the discharge coefficient to be used to determine the rate of change of the diverted discharge. We use such distributions to derive a physically based relationship relating the overall diverted discharge to the length of the rack, the void ratio, the discharge coefficient measured under static conditions, the specific head of the stream approaching the rack, and a modified Froude number. The robustness of the proposed relationship is confirmed by the comparison between the discharges calculated through the proposed relationship and those measured in an extensive series of experiments available in the literature, characterized by ranges of the relevant flow parameters much larger than those investigated in the present contribution.
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Acknowledgments
The writers were grateful to Fabio Sartori and Alessandra Tambara of University of Trento (Italy), Department of Civil and Environmental Engineering for the profitable cooperation during the laboratory measurements.
References
Bouvard, M. (1953). “Debit d’une grille par en dessous (Discharge passing through a bottom grid.” Houille Blanche, 3, 290–291.
Bouvard, M. (1992). “Mobile barrages and intakes on sediment transporting rivers.” IAHR Monograph, Balkema, Rotterdam, The Netherlands.
Brunella, S., Hager, W. H., and Minor, H.-E. (2003). “Hydraulics of bottom rack intake.” J. Hydraul. Eng., 129(1), 2–10.
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.
De Marchi, G. (1947). “Profili longitudinali della superficie libera delle correnti permanenti lineari con portata progressivamente crescente e progressivamente decrescente entro canali a sezione costante.” Ric. Sci. (in Italian).
Ferro, V. (1992). “Flow measurement with rectangular free overfall.” J. Irrig. Drain. Eng., 118(6), 956–964.
Garot, F. (1939). “De Watervang met liggend rooster.” Ing. Ned. Indie, 7.
Hager, W. H. (1983). “Hydraulics of plane free overfall.” J. Hydraul. Eng., 109(12), 1683–1697.
Henderson, F. M. N. (1966). Open channel flow, MacMillan, New York.
Khan, A. A., and Steffler, P. M. (1996). “Modeling overfalls using vertically averaged and moment equations.” J. Hydraul. Eng., 122(7), 397–402.
Kuntzmann, J., and Bouvard, M. (1954). “Etudes teoretique des grilles de prises d’eau du type ‘En-Dessous’ (Theoretical studies of bottom type water intake grids).” Houille Blanche, 5, 569–574.
Marchi, E. (1993). “On the free overfall.” J. Hydraul. Res., 31(6), 777–790.
Mizuyama, T., and Mizuno, H. (1994). “Behavior of debris flow at control structures.” Proc., IAHR Int. Workshop on Floods and Inundations Related to Large Earth Movements, C2.1–C2.12.
Mostkow, M. (1957). “Sur le calcul des grilles de prise d’eau (Theoretical study of bottom type water intake).” Houille Blanche, 4, 570–580.
Nasser, M. S., Venkataraman, P., and Ramamurthy, A. S. (1980). “Flow in channel with a slot in the bed.” J. Hydraul. Res., 18(4), 359–367.
Noseda, G. (1955). “Operation and design of bottom intake racks.” Proc., VI General Meeting IAHR, Vol. 3, The Hague, C17-1-C17-11.
Noseda, G. (1956a). “Correnti permanenti con portata progressivamente decrescente, defluenti su griglie di fondo.” Energ. Elettr., 1, 41–51 (in Italian).
Noseda, G. (1956b). “Correnti permanenti con portata progressivamente decrescente, defluenti su griglie di fondo.” Energ. Elettr., 6, 565–581 (in Italian).
Oliveto, G., Biggiero, V., and Hager, W. (1997). “Bottom outlet for sewers.” J. Irrig. Drain. Eng., 123(4), 246–252.
Orth, J., Chardonnet, E., and Meynardi, G. (1954). “Etude de grilles pour prises d’eau du type ‘en-dessous’ (Study of bottom type water intake grids).” Houille Blanche, 3, 343–351.
Righetti, M., Rigon, R., and Lanzoni, S. (2000) “Indagine sperimentale del deflusso attraverso una griglia di fondo a barre longitudinali.” Proc., XXVII Convegno di Idraulica e Costruzioni Idrauliche, Vol. 3, Genova, Italy, 112–119 (in Italian).
Venkataraman, P., Nasser, M. S., and Ramamurthy, A. S. (1979). “Flow behavior in power channels with bottom diversion works.” Proc., XVIII IAHR Conf., Vol. 4, Cagliari, Italy, 115–122.
Viparelli, C. (1963). “Dissipatori a griglia di fondo.” Energ. Elettr., 7, 509–519 (in Italian).
Yen, B. C., and Wenzel, H. G. (1970). “Dynamic equations for steady spatially varied flow.” J. Hydr. Div., 96(3), 801–814.
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Published In
Journal of Hydraulic Engineering
Volume 134 • Issue 1 • January 2008
Pages: 15 - 22
Copyright
© 2008 ASCE.
History
Received: Jan 13, 2006
Accepted: Jul 3, 2007
Published online: Jan 1, 2008
Published in print: Jan 2008
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