166 EFFLUX THROUGH SHORT TUBES, OK AJUTAGES. 



different degrees of advantage in this respect, which can be 

 determined only by experiment. The discharge is found to 

 be greater when the ajutage is conical and the larger end 

 is the discharging orifice. 



(1) The results of many experiments* made with cylin- 

 drical tubes 1 to 3 inches in diameter, the length of which 

 does not exceed 4 times the diameter, as in 



Fig. 48, and under a head of water varying 

 from 3 to 20 feet, give as a mean value of 

 the coefficient of efflux, /< = .815, or about 

 . Since the coefficient of efflux for a sim- 

 ple orifice in a thin plate (Art. 94) is p = 

 .615, it follows that, when the other circum- 

 stances are the same, the discharge through 



a short cylindrical tube = ' = 1.325 times the discharge 



.010 



through a simple orifice in a thin plate. These coefficients 

 increase a little when the diameter of the tube becomes 

 greater, and decrease a little when the head of water or the 

 velocity of efflux increases. 



In this tube, the contraction of the stream takes place at 

 the inlet ab, and not at the outlet. If a small hole were 

 bored in the tube at a or b, no water would run out, but air 

 would be sucked in ; and when the hole is enlarged, or when 

 several of them are made, the discharge with a filled tube 

 ceases. Also, if a tube be placed in a vessel of water A, and 

 inserted in the hole at b, the water will rise in the tube Ab, 

 and run out of the tube abed. 



(2) With a compound mouth-piece, having 

 an enlargement at its exterior orifice or out- 

 let, as well as at its interior orifice, as in Fig. 

 49, the results of careful experiments f give 

 the coefficient of efflux /* = 1.5526, when the 

 narrow part cd is treated as the orifice, thus Fi 9- 



Experiments made by Michelotti. 



t Made b7 Eytelwein, 



