GENERAL PRINCIPLES OF HYDRAULICS 459 
v, be the pressure and velocity of the jet at AB. P, the pressure of 
the water at EF, will be the same as that of the atmosphere. 
The coefficient of contraction at AB is 
k 
Between AB and EF there is a loss of energy 
or head (Art. 395) equal to 
J (v, put oy y2 1 1) 
29 g\k SO) 
| If ¢ is the coefficient of velocity at AB, 
then v, =c¢ ,/2gh, and the energy at AB is 
~ se ai, 
E k, and », “s 
h 
Fia. 754. 
The energy at EF is ¥ Hence c%h = ?— + ¥ € 
si 2g ~ 29° 2g\k 
it follows that 
¢ /2gh ¢ 
v= 
pea VeG=)} 
| af {l+(5-1 1+(7-1 
is the coefficient of velocity and also the coefficient of discharge at EF, 
since the jet fills the pipe at EF. 
Taking c= 0°97, and k= 0°63 for a sharp-edged orifice, 
C= ont = 0-836. 
Ieee) 
_ Experiments with mouthpieces having lengths from two to three times 
the diameter gave C=0°82. It should be noted that in the foregoing 
investigation the effect of friction in the pipe has been neglected, but 
__ the pipe being short, this effect will be small. 
. 
- 1). From which 
=C ,/2gh, where C = 
. P, vw? P w wv/il 2 
By B Bor Pw De bi H 
By ernoulli’s theorem = He 29 hs aq* 55k 1 ence 
Ae 1). Tpetiiia fore ita value C./IGh, 13 = acea(t . 1). 
w gk 7 w k 
» P-p, #0 
7 
| If a vertical tube be inserted into the mouthpiece at B, and its lower 
end be placed in a vessel open to the atmosphere and containing water, 
water will rise in this tube to a height A’, given by the equation 
| 1 
- Zhi x 
P-P (: ) 2e%A( 1) 
Mme e 30s 1a 
w l 
1+(;-1) 
k 
Taking c=0°97, and /=0°63 as before, the above reduces to 
h'=0°82h. By experiment h’ is about 3h, which corresponds to C = 0°82, 
and k= 0°64. 
