FLOW OF WATER IN CHANNELS AND PIPES. 59 



have a pipe of diameter d ft., under a pressure or head 

 h ft., its total length being L, also in feet, the velocity 

 in that pipe in feet per second is 



. . . (.2) 



Now the flow of water in a pipe is of course depend- 

 ent upon the friction in that pipe, and the friction is 

 proportional to 



1. Length of pipe. 



2. Inversely as diameter. 



3. The velocity squared. 



4. The roughness. 



5. Independent of pressure. 



Now when the velocity V is found, and we know 

 the sectional area, the discharge in cub. ft. is easily 

 found. Multiply this by 6*25 and we have gallons. 

 Then if we have 



G = gallons discharge per minute, 

 L = length of pipe line in yards, 

 D = diameter of pipe in inches, 



we can find the loss of head due to friction by the 

 equation 



j~+ .1 T 



H = loss of head in ft. = /~~Tyr5 ( J 3) 



Or if it is a pipe line for a power scheme, the loss of 

 power would be a more important quantity. 



Then if H* = the loss of energy in foot-lbs. of every 

 pound of water passing through the pipe, L = length, 

 and D = diameter of pipe in feet, and V as already 

 calculated, 



TT 0007LV' 2 f x 



Hi - . . . (14) 



