Rack Length in Bottom Intake Systems

Rack Length in Bottom Intake Systems

Luis G. Castillo Juan T. García Patricia Haro José M. Carrillo

Departamento de Ingeniería Civil, Universidad Politécnica de Cartagena, Spain

Departamento de Ingeniería Civil y Ambiental, Escuela Politécnica Nacional, Ecuador

Page: 
279–287
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DOI: 
https://doi.org/10.2495/EI-V1-N3-279-287
Received: 
N/A
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Revised: 
N/A
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Accepted: 
N/A
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Available online: 
N/A
| Citation

OPEN ACCESS

Abstract: 

Bottom intake systems, made by racks longitudinally disposed in the flow direction, are classically used to derive mean flows in continuous mountain rivers with intensive sediment transport. They are known as Caucasian or Tyrolean Intakes. Nowadays, works are also being addressed to study these intakes in order to derive flash floods from ephemeral rivers in semiarid zones to collect runoff and improve the availability of resources. In the design of bottom intake systems, the length of rack is an important variable. This article includes several formulations that come from experimental works in laboratory and in prototype. The objective is to complement and update those works, including some empirical expressions proposed and experimental works developed since 2010 at the Universidad Politécnica de Cartagena. Rack length values for different flow rates are presented in dimensionless form (L/h  – required rack length over critical depth) for the spacing area ratio over total area (void fraction m) of values 0.12, 0.28 and 0.60. These lengths present important differences depending on the conditions for which they were obtained, for example type of bars (circular or flat), spacing between the bars or the slope adopted by the rack. Values of the dimensionless rack length considering obstruction factors are also analysed. The Froude similitude criterion has been considered to obtain prototype values from the laboratory experimental conditions.

Keywords: 

bottom racks, design conditions, rack length, sediment transport, void ratio

  References

[1] Krochin, S., Diseño Hidráulico. Segunda. Escuela Politécnica Nacional: Quito, 1978.

[2] García, J.T., Estudio experimental y numérico de los sistemas de captación de fondo. Ph.D. Thesis, Universidad Politécnica de Cartagena, 2016 (in Spanish).

[3] Castillo, L.G., García, J.T. & Carrillo, J.M., Experimental and numerical study of bottom rack occlusion by flow with gravel-sized sediment. Application to ephemeral streams in semi-arid regions. Water, 8, p. 166, 2016. DOI: 10.3390/w8040166.

[4] Castillo, L.G. & Lima, P., Análisis del Dimensionamiento de la Longitud de Reja en una Captación de Fondo. Proceedings of the XXIV Congreso Latinoamericano de Hidráulica, Punta del Este, 2010.

[5] Drobir, H., Kienberger, V. & Krouzecky, N., The wetted rack length of the Tyrolean weir. Proceedings of the IAHR-28th Congress, Graz, 1999.

[6] Frank, J., Fortschritte in der hydraulic des Sohlenrechens. Bauingenieur, 34, pp. 12–18, 1959 (in German).

[7] Bouvard, M. & Kuntzmann, J., Étude théorique des grilles de prises d’eau du type (En Dessous). Houille Blanche, 5, pp. 569–574, 1956 (in French). DOI: 10.1051/lhb/1954049.

[8] Noseda, G., Correnti permanenti con portata progressivamente decrescente, defluenti su griglie di fondo. L’ Energia Elettrica, 33, pp. 41–51, 1956 (in Italian).

[9] Brunella, S., Hager, W.H. & Minor, H.-E., Hydraulics of bottom rack intake. Journal of Hydraulic Engineering, 129, pp. 2–10, 2003. DOI: 10.1061/(ASCE)0733-9429(2003)129:1(2).

[10] Jiménez, Ó & Vargas, O.A., Some experiences in the performance of bottom intakes. Proceedings of the International Symposium on Hydraulic Structures, IAHR: Guayana, 2006.

[11] Orth, J., Chardonnet, E. & Meynardi, G., Étude de Grilles Pour Prises d’Eau du Type «  En Dessous ». La Houille Blanche, 3, pp. 343–351, 1954 (in French). DOI: 10.1051/lhb/1954034.

[12] Castillo, L.G., García, J.T. & Carrillo, J.M., Influence of rack slope and approaching conditions in bottom intake systems. Water, 9, p. 65, 2017. DOI: 10.3390/W9010065.

[13] Melik-Nubarow, S.G., Type perfectionnè de prise d’eau à grille horizontale. Revue, N10–N11, 1939 (in French).

[14] Drobir, H., Entwurf vonWasserfassungen im Hochgebirge. Österreichische Wasserwirtsch, 11, pp. 243–253, 1981 (in German).

[15] Righetti, M. & Lanzoni, S., Experimental study of the flow field over bottom intake racks. Journal of Hydraulic Engineering, 134, pp. 15–22, 2008. DOI: 10.1061/(ASCE)0733-9429(2008)134:1(15).

[16] Henderson, F.M.N., Open Channel Flow, MacMillan: New York, NY, 1966.