354 



HYDEAULICS AND ITS APPLICATIONS 



These observations are recorded for a series of verticals in the cross 

 section. They are then plotted on squared paper, depths as ordinates 

 and velocities as abscissae, and a smooth curve is drawn through the 

 plotted points, care being taken to give them as nearly as possible equal 

 weight if they do not all fall on a smooth curve. From this curve 

 velocities are read off at top and bottom and at equal intervals of, say, 

 each '5 foot, and are set down in order. Thus from the above curve we 

 get 



O'O 

 0-5 

 1-0 

 1-5 



v a = 2-90 



2-0 

 2-5 



v = 2'25 

 v 5 = 1-88 

 v b = 1-31 



4 



n = 2-88 

 ?-a = 2-77 



r 3 = 2-58 



The mean velocity in this vertical is then computed from the pris 

 moidal formula for seven abscissae as follows : 



v m = A { v. +'r 6 + 4 (v t + r 8 + r 6 ) + 2 (r a + i> 4 ) } 

 In this case we have : 



v s + r b = 2-90 + 1-81 = 4-21 

 = 4 { 2-88 

 = 29-36 

 = 2 (2'77 

 = 10-04 



4-21 + 29-36 + 10-04 } 

 = 2-42 f.s. 



The cross section having been plotted, the areas of the various com- 

 partments having such verticals as their centre lines may be obtained, 

 either by direct measurement by planimeter or by calculation, and the 

 discharge calculated as follows : 



+ r 8 + 

 + r 4 ) 



2*58 + 1'88 

 2'25) 



Total ... 311-0 c.f.s. 



When the vertical velocity curves have been obtained the discharge may 





