THE FLOW OF WATER IN WOOD-STAVE PIPE. 59 
less any velocity head, h/, 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 
H E = h v + he + h f -h/ (21) 
where H E has the significance shown in figure 1 and h v , he, h f , and 
h/ 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 slight 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 hydraulics. 
VELOCITY AND ENTRY LOSSES. 
In designing pipes of small diameter and great length, the losses 
due to velocity and entry heads, h v and he, 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 fine 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, 
h v , necessary to create a given velocity is shown in column 2, Table 5. 
The entry loss will be from 0.5 h v where the pipe of standard size 
begins at a headwall and is without bell or taper mouth, to about 
0.25 h v for a rounded intake, and 0.05 h v for a bell-mouth intake. 
Many of the structures built by the United States Reclamation 
