Analyses Of Minimum Submergence And Air Discharge In Vertical Shafts With Different Inlets

Intakes and dropshafts conduct water from the inlet towards a vertical shaft connecting to a tunnel, which has the function of discharging to a hydroelectric power plant, irrigation or water supply system. A problem to the hydraulic engineer is to design an intake taking into account the prevention of vortex formation. Vortex with air entrainment can carry away less efficiency of hydraulic machines, reduction of discharge coefficients and vibration. Critical submergence is one of the factors that most influences vortex formation. This study has the objective of investigating minimum submergence conditions in vertical intakes and air entrainment. An experimental study has been conducted through different vertical intake diameters, varying the intake height, submergence and flow. Vortices were classified from low intensity ones with superficial swirl and no depression, to strong ones with air entrainment. The study also compares different inlet types and flow condition, showing that the air entrainment depends on the geometry inlet, being great for radial ones. Results showed that in order to avoid vortices with air entrainment the minimum necessary rate of submergence to intake diameter should be 0, 7. It was determined the discharge coefficient for vertical intakes with and without vortex formation and also an evaluation of air entrainment was done.20472052China Society for Hydropower Engineering,Chinese Hydraulic Engineering Society,et al.,Int. Assoc. Hydraulic Eng. Res. (IAHR),National Natural Science Foundation of China,State Key Lab. Hydrology-Water Resources Hydraulic Eng.Almeida, A.B., (2006) Sistemas Elevatórios e HidroelétricosAnwar, H.O., Formation of a weak vortex (1966) Journal of Hydraulic Research, 4 (1), pp. 1-16Azevedo Netto, J.M., Sistemas prediais de hidráulica aplicada (1987) Hydraulic Manual, , Ed. Edgard Blücher, São Paulo, Brasil (in portuguese)Castro, M., Estudio Experimental sobre la estructura de entrada de un descargador a vórtice (1988) XIII Congresso Latinoamericano de Hidraulica, , La Habana, CubaDaggett, L.L., Keulegan, G.H., Similitude in free surface vortex formation (1974) Journal of Hydraulic Division, 100 (11), pp. 1565-1581Ferreira, L.M.C., (2001) Vortex Formation in Vertical Intakes, , Dissertação apresentada à FEC da UNICAMP para obtenção do título de Mestre em Engenharia Civil, Campinas, SPFais, L.M.C.F., (2007) Análise Experimental Da Curva de Ligação Poço-túnel Em Poços Verticais Com Emboque Tipo Tulipa, , Tese apresentada à FEC da UNICAMP para obtenção do título de Doutor em Engenharia Civil, Campinas, SPFerreira, L.M.C., Borin, D., Genovez, A.I.B., Critical submergence in vortex formation in vertical intakes (2000) XIX Congresso Latinoamericano de Hidráulica, 2, pp. 673-680. , Cordoba, 22 al 27 oct, 2000 (in portuguese)Ferreira, L.M.C., Genovez, A.I.B., Air entrainment analysis in vertical shafts with different inlets (2005) Water Resources Brazilian Simposium, 26. , 2005, João Pessoa, Paraíba. (CR-ROM), João Pessoa, 20 a 24 nov 2005 (in portuguese)Ferreira, L.M.C., Genovez, A.I.B., Minimun submergence in vertical water intakes (2005) Ingeniería del Agua, 12 (2), pp. 107-115. , (in portuguese)Genovez, A.I.B., (1997) Evaluation of Limit Lenght in the Study of Air Entrainment in Shaft with Morning Glory Entrance, , Associate Professor Tesis, UNICAMP. Campinas, Brazil. (in Portuguese)Gulick, F.S., Numerical simulation of a free surface vortex formed in the wake of a pier at a hydropower intake (2007) 32 IAHR Congress, , Veneza, Italia, july 2007Gulliver, J.S., Rindels, A.J., Lindblom, K.C., Designing intakes to avoid free-surface vortices (1986) International Water Power & Dam Construction, 38 (9), pp. 24-28Jain, S., Tangencial vortex inlet (1988) Journal of Hydraulics Engineering, 114Padmanabhan, M.E., Hecker, G.E., Scale efects in pump sump models (1983) Journal of Hydraulic Engineering, 110 (11), pp. 1540-1556Kocabas, F., Yildirim, N., Effect of circulationon critical submergence o fan intake pipe (2002) J Hyd Research, 40 (6), pp. 741-752Hager, W., Kellenberger, M., Die dimensionierung des wirbelfallschachtes (1987) Wasser-Abwasser, 128 (11), pp. 852-590Ye, M., Relationship between vortex core radius and water-surface curvature characteristic radius (2007) 32 IAHR Congress, , Veneza, Italia, july 2007Zhao, C., Experimental study of flow in a vortex drop shaft (2006) Journal of Hydraulic Engineering, 132 (1), pp. 61-6