60 



BULLETIN 376, U'. S. DEPAETMENT OF AGRICULTURE. 



Service were designed with the entry loss taken as half the velocity 

 head, even though there were more or less rounding and taper in the 

 intake structures. In Table 5, column 3, is shown the amount of 

 entry loss when taken as haK the velocity head (column 2); and the 

 sum of the entry and velocity losses is shown in column 4. 



Table 5. — Mean velocity in pipe, V, in feet per second; and head of elevation lost creating 

 this velocity and overcoming entrance conditions, hp-\-hg, in feet. 



1 



2 



3 



4 



1 



2 



3 



4 



v 



hv 



he 



hv+he 



v 



hv 



he 



hv+he 



Ft.persec. 



Feet. 



Feet. 



Feet. 



Ft.persec. 



Feet. 



Feet. 



Feet. 



1.0 



0.016 



0.008 



0.024 



5.0 



0.389 



0.195 



0.584 



.2 



.022 



.011 



.033 



.2 



.420 



.210 



.630 



.4 



.030 



.015 



.045 



.4 



.453 



.227 



.680 



.6 



.040 



.020 



.060 



.6 



.488 



.244 



.732 



.8 



.050 



.025 



.075 



.8 



.523 



.262 



.785 



2.0 



.062 



.031 



.093 



6.0 



.560 



.280 



.840 



.2 



.075 



.037 



.112 



.2 



.598 



.299 



.897 



.4 



.090 



.045 



.135 



.4 



.637 



.319 



.956 



.6 



.105 



.053 



.158 



.6 



.677 



.339 



1.016 



.8 



.122 



.061 



.183 



.8 



.719 



.359 



1.078 



3.0 



.140 



.070 



.210 



7.0 



.762 



.381 



1.143 



.2 



.159 



.080 



.239 



.2 



.806 



.403 



1.209 



.4 



.180 



.090 



.270 



.4 



.851 



.426 



1.277 



.6 



.202 



.101 



.303 



.6 



.898 



.449 



1.347 



.8 



.224 



.112 



.336 



.8 



.946 



.473 



1.419 



'4.0 



.249 



.125 



.374 



8.0 



.995 



.498 



1.493 



.2 



.274 



.137 



.411 



.2 



1.045 



.523 



1.568 



.4 



.301 



.151 



.452 



.4 



1.097 



.549 



1.646 



.6 



.329 



.165 



.494 



.6 



1.150 



.575 



1.725 



.8 



.358 



.179 



.537 



.8 



1.204 



.602 



1.806 



Where the usual types of inlet and outlet structures are employed, 

 with but little construction and consequent expense incurred for con- 

 servation of entry and velocity heads it is recommended that the 

 figures in Table 5 be used. In that case any influence on the total 

 loss of head, derived from the rate of flow toward the intake as in 

 condition 2, where water enters the pipe from an open channel, wiU 

 introduce a small factor of safety for conservative construction. 

 The same may be said of any slight recovered velocity head where 

 the pipe discharges into an open channel. 



In figure 1, Plate XII, probably the most common form of con- 

 struction for both inlet and outlet of a wood-stave siphon is shown. 

 In some cases taper staves are used in both inlet and outlet, so that 

 the velocity is gradually increased in entering the pipe, thus reduc- 

 ing the entry loss. This construction classes the pipe under 

 condition 3. The velocity is gradually decreased at the outlet, 

 preserving the velocity head. The usual practice in this type of con- 

 struction is to place the center of the pipe opening for the inlet cham- 

 ber at or below the bottom of the leading canal. The pipe at the 

 outlet is usually placed so that the top of the opening is sHghtly 

 below the high-water line at full capacity. 



