THE FLOW OF WATER IN WOOD-STAVE PIPE. 5' 



The amouiit of loss at the entry, due to the effect of contraction 

 eddies and other retarding influences, is variable and uncertain, but 

 most authorities agree that it should be taken as half the velocity head 

 unless the inlet structure is especially designed to minimize this loss. 

 For further discussion see page 59. 



Friction head, hf, is that lost in overcoming the retarding in- 

 fluences within a reasonably straight pipe. In pipes of great length, 

 the amount of this loss so far exceeds the two l®sses first mentioned 

 that they may often be neglected, especially in small pipes. This 

 is the loss upon which the experiments described in this paper were 

 concentrated. Apart from all other losses of head it must be found 

 in order to permit solution of the various formulas for the flow of 

 water in pipes with the view to securing additional values for the 

 factor representing the retarding influences designated as friction. 



In addition to the above losses, there may be others, such as those 

 due to bends and valves or other obstructions; but, as a general thing, 

 these items do not enter the design of wood-stave pipes, especially 

 for irrigation purposes. In this use the pipe is laid on such gentle 

 curves, both horizontal and vertical, that such losses need not be 

 considered. Valves are seldom set across the line of the pipe, 

 although there are often one or more valves of various sizes leading 

 from the pipe. The loss in the main line due to these valves is 

 also nfeghgible compared with the friction and velocity head losses. 



In 1775, Chezy, a French engineer, offered his now weU-known 

 formula for the flow of water in both open channels and closed 

 conduits : 



V = CVK (3) 



Here C is a coefficient, originally thought to be constant, but now 

 known to vary with functions of the slope, the hydrauUc radius, the 

 velocity, and with some factor representing the retarding influences 

 in the channel. Many of the formulas used in this country for the 

 design of pipes have accepted the Chezy formula as a basis and made 

 only such modifications as experience dictated, some of them merely 

 assigning definite values to the coefficient C for definite conditions of 

 velocity, roughness, and size of pipe. 



Since the hydrauUc elements secured in the field experiments fur- 

 nish the necessary data for the determination of the factor repre- 

 senting the retarding influences in all the formulas most used in this 

 country, this publication will show this factor as developed by field 

 tests for several formulas as f oUows : 



{a) The Chezy formula, 3 on page — , 



V = CVH^ = CIl°-V°^ • (4) 



