UNIFORM PIPE CONNECTING TWO RESERVOIRS. 189 



and 



7> 



or 



where the constants ft and /are to be determined by experi- 

 ment. 



When v and d are given, (2) is used to determine A; when 

 h and rf are given, (4) is used to determine v. 



COR. 1. If the pipe is bell-mouthed, ft is about .08. If 

 the entrance to the pipe is cylindrical, ft = 0.505. Hence, 

 1 + ft = 1.08 to 1.505. In general, this is so small com- 

 pared with f-j that for practical calculations it may be 



neglected ; i. e., the losses of head, except the loss in sur- 

 face friction, are neglected. It is only in short pipes and 

 at high velocities that it is necessary to take account of the 

 term (1 + 13). For instance, in pipes for the supply of tur- 

 bines, v is usually limited to 2 feet per second, and the pipe 

 is bell-mouthed. In this case, we have 



(1 + 0) = 1.08 x 4 x .0155 = 0.067 foot* 

 *9 



In pipes for the supply of towns, v may range from 2 to 

 4^ feet per second, and then we have 



(1 + 0) o.l to 0.5 foot. 

 'Kg 



In either case, this amount of head is small compared 



* i = .0165 foot. 



