132 



HYDRAULICS AND ITS APPLICATIONS 



The following table gives the approximate values of C for circula 

 orifices (Hamilton Smith) : 



ART. 51. SUBMERGED ORIFICES. 



If the water level on the discharge side is above the highest point c 

 the opening we get a submerged orifice. 



Let HI = depth of water above upper edge of orifice on the incomin 

 side, in feet. 



Let HZ = similar depth on discharge side. 



Then the effective depth at all points in the orifice is the same, viz 

 Hi - H 2 (p. 108). 



.*. Theoretical velocity of efflux = \/2 g (Hi Hz) ft. sec. 



.'. Quantity per second through orifice = C A V% g V ' H\ H- 

 where A is the area of the orifice. 



Taking into account the velocity of approach, vi, the effective head wil 



T 2 



now be HI -\- h HZ feet, where h = ^~ an( ^ ^he discharge will b 



given by 



Q = C A V%~g V HI -\- h HZ cub. ft. sec. 



The value of G for a submerged orifice may be taken as being abou 

 1 per cent, less than its value for the same orifice under the same effectiv 

 head, and when discharging freely into air. 



Haribury Brown l gives the following as being approximate values o 

 C for sluices and regulator openings in masonry piers : 



1 " Irrigation," Constable & Co.. London, 1907. 



