488 EXPERIMENT STATION RECOED. [Vol.36 



Summary of results of tests of irrigation pumping plants. 



Experiments with submerged orifices and tubes, T. C. Rogeus and T. L. 

 Smith {Engin. Neics, 76 {1916), No. 18, pp. 825-827, figs. S).— Exneriments 

 conducted at Cornell University on the flow of water through orifices 6, 8, and 

 10 in. square under heads up to 2.2 ft. are reported. The length of the tube 

 was varied, but square edges at the entrance were used throughout. 



" Curves were plotted between discharge coefficient and head for each length 

 of tube and also between average discharge coefficient and length of tube, the 

 latter being expressed as the ratio of tube length L to the side of the square 

 orifice D. The curves plotted showing variation of discharge coeflficient with 

 head indicate that in most cases there is a slight increase in coefficient with 

 higher heads. This increase is not pronounced, however, except in one or two 

 curves, and in some cases there seems to be a decrease in the coefficient with 

 higher heads. . . . 



" The general conclusion may be drawTi from these experiments that an- 

 nexing a tube to a submerged square orifice will greatly increase its flow under 

 a given head until the length of tube is equal to about 1.5 times the side 

 of the square. A longer tube will not decrease the flow, unless the friction is 

 large, but it will not materially increase it. For free discharge into the air the 

 coefficient does not vary, but remains at about 0.61, whatever the tube length. 

 This value is about 0.67 per cent greater than the submerged sharp-edge co- 

 efficient, and corresponds to the submerged coefficient for L/D = 0.05. From 

 this it follows that, given a square orifice with a tube attached and a fixed 

 head of water upstream, a greater quantity may be made to flow through the 

 orifice by submerging the dowTistream side than will flow if the orifice dis- 

 charges into the air. This fact was verified by experimentation." 



