SUDDEN CONTRACTION OF SECTION. 



201 



109. Sudden Contraction of Section. When water 

 passes from a larger to a smaller section, as in Figs. 56, 57, 

 where it passes from the pipe AB into 

 the narrower pipe CEDF, a contraction 

 is formed, and the contracted stream 

 abruptly expands to fill the section of 

 the pipe, thereby causing a loss of head 

 by this sudden enlargement, precisely as 

 in Art. 108. 



(1) Let a be the area of the section 



and v the velocity of the stream at EF. Then, if c is the 

 coefficient of contraction, the section of the stream at CD 

 will be ca, and the velocity V at this section will be found 

 by means of the formula 



v'ca = va\ 



Hence, the loss of head in passing from CD to EF is 



p v 



/I \ 2 

 if is put for ( 1 ) 



\C ' 



If c is taken = 0.64 (Art. 92), we have 



7)2 



which in (1) gives A, = 0.316 ^- 



(2) 



Sen. 1. The value of the coefficient of contraction in 

 this case is, however, not well ascertained, and the result is 



