THE PLOW OF WATEE. IK WOOD-STAVE PIPE. 59 



less any velocity head, hy', that may be recovered as the water 

 approaches the pipe outlet at a velocity relatively high compared 

 with the velocity in the open water below the outlet chamber. This 

 total may be expressed by the formula 



HE = hv + he + h,-h/ (21) 



where He has the significance shown in figure 1 and hv, he, hf, and 

 hv' have the significance defined on page 3. The influence of 

 gentle curves was included in the data upon which the formulas were 

 based, so that an additional loss for sHght bends or curves need not 

 be considered in the design of the usual pipe on irrigation systems. 

 If sharp bends can not be avoided then an additional loss of head 

 must be anticipated. The results of such tests as have been made 

 on bends in pipes are given in standard works on hydrauhcs. 



VELOCITY AND ENTRY LOSSES. 



In designing pipes of small diameter and great length, the losses 

 due to velocity and entry heads, hy and h©, are so small compared 

 with the friction loss that they may be neglected. Otherwise they 

 should be included in the allowance for total lost head. 



As a rule a wood-stave pipe line begins under one of four general 

 conditions : 



1. Intake chamber located in a reservoir, where the velocity of the 

 water is practically zero. No taper or transition section between 

 intake and pipe. 



2. Intake chamber located on an open channel where there is an 

 appreciable velocity toward the structure but where this velocity 

 is not available because a bend or well at the intake practically 

 dissipates the velocity head. 



3. Intake chamber followed by a transition section in which the 

 velocity is increased over that existing in the leading channel or 

 reservoir. The outlet end of a pipe beginning under this condition 

 is usually provided with a similar transition section. 



4. The wood pipe but a continuation of another pipe of the same 

 size but of concrete, steel, or other material. In this case there is 

 little or no loss due to entry or velocity, the only factor introduced 

 being the change in friction head due to change of material. 



In conditions 1 and 2 it is best to consider the water above the 

 intake as at rest. From this state of rest velocity must be created and 

 increased to the mean velocity, V, existing in the pipe. The head, 

 hv, necessary to create a given velocity is shown in column 2, Table 5. 

 The entry loss will be from 0.5 hy where the pipe of standard size 

 begins at a headwaU and is without beU or taper mouth, to about 

 0.25 hv for a rounded intake, and 0.05 hv for a bell-mouth intake. 

 Many of the structures built by the United States Reclamation 



