380 



HYDRAULICS AND ITS APPLICATIONS 



/. Resultant pressure on vane acts in the direction C A and is of 



W Q 



magnitude . C A Ibs. 



(2) Impact on One of a Scries of Moving Vanes. 



Let BA (Fig. 171 a and b) represent the initial velocity of the jet in 

 magnitude and direction. 



Let EC represent the velocity of the vane. 



Then CA represents the relative velocity of the water over the surface 

 of the vane. 



Draw E F = C A tangential to the vane at exit and make F G equal 

 and parallel to B C. The vector l^G, which represents the velocity com- 



Fltt. 171. 



pounded of the velocity of the vane and of that of the water relative to 

 the vane, now gives the absolute velocity of the discharge stream. 



Drawing B H equal and parallel to E G, the acceleration which is given 

 to the water by the vane is represented by A H, and the resultant pressure 



W Q 

 on the vane P = - - . HA Ibs. The line of action of this pressure 



is parallel to HA. 



The effective pressure is the component of this in the direction of 



JJ7 Q . 



motion of the vane. Thus in Fig. 171 a, this is given by - - . LM Ibs., 



]y Q 



and the work done per second by - - . LM . BC ft. Ibs. In Fig. 171 b, 



