EFFLUX THROUGH SHORT TUBES, OR AJUTAGES. 165 



The ratio of the actual discharge Q z to the theoretical 

 discharge Q is called the Coefficient of Efflux. 



Denoting the coefficient of efflux by /A, we have, from (1) 

 and (6) of Art. 76, 



p = Sl=:0 = .6a; (2) 



i. e., the coefficient of efflux is the product of the coef- 

 ficient of velocity and the coefficient of contraction. 



SCH. The value of n can also be determined by direct 

 measurement of the discharge in a given time, an observa- 

 tion which can be made with much greater accuracy than 

 those of contraction and velocity, on which it depends. In 

 the present case it is found by direct measurement to be .62, 

 agreeing well with the product .64 x .97, of the values above 

 given.* 



REM. Repeated observations and experiments have led to the con- 

 clusion that the coefficient of efflux is not constant for all orifices iu 

 thin plates ; that it is greater for small orifices and small velocities of 

 efflux than for large orifices and great velocities, and that it is much 

 greater for long narrow orifices than for those whose forms are regu- 

 lar or circular. For square orifices, whose areas are from 1 to 9 square 

 inches, under a head of from 7 to 21 feet, according to the experiments 

 of Bossut and Michelotti, the mean coefficient of efflux is // = .610 ; 

 for circular orifices from | to 6 inches in diameter, with from 4 to 20 

 feet head of water, it is ft = .615. or about T \.f 



95. Efflux through Short Tubes, or Ajutages. 



If the water, instead of flowing through an orifice in a thin 

 plate, be allowed to discharge through short tubes, called 

 also ajutages and mouth-piece*, the quantity discharged from 

 a given orifice is considerably increased. More seems to be 

 gained by the adhesion of the liquid particles to the sides of 

 the tube, in preventing the contraction of the stream, than 

 is lost by the friction. Ajutages of different forms have 



* CotterilPs Applied Mechg., p. 449. 



t Weisbach's Mecbs., p. 824 ; also, Tale's Mecb. Phil., p. 982. 



