274 



HYDRAULICS AND ITS APPLICATIONS 



shall fall below the hydraulic gradient, and in such cases a. syphon 

 (Fig. 122) is commonly used. 



In its simplest form this consists of an inverted U-tube (Fig. 123), 

 both legs being full of water, and the flow is generally calculated by 

 equating the total head producing flow, i.e., the head due to the un- 

 balanced column of water Z A Z C , or the difference of heads in the two 

 reservoirs, to the sum of the frictional and other losses in the pipe and 

 of the velocity head produced. 



f 7 2 



Thus Z A /^c" l ss 

 length of the syphon A' B C'. 



entrance and exit 





, I being the total 



FIG. 122. 



This may be seen by considering the flow along each leg of the syphon 

 separately. 



Along A' B, we have 



Z E + -- + + loss at entrance, 



W 2 g 2 g m 



Along B C' we have 



*+ 



+ - 



20 



/ 





W 



Igm 



.'. Z B Z c , -f -j|r= -~ 



.*. From (1) and (2) we get on adding 



7 7 _ PC- PA' _, J?__ 



** **~ -gr~ -+ 2 <7 



(2) 



