IMPACT OF JETS 



369 



Again, the initial momentum, in a direction perpendicular to the plane 



II t v 2 



- . sin 6, and the final momentum in this direction = 0. 

 9 



W t 



Normal pressure on plane = 



.'. Pressure in direction of jet = 



W t 





. - . . 

 sm a IDS. 



sin 2 Ibs. 



Impact on Stationary Curved Vane (Fig. 165). 



If the inclined plane of the previous case be fitted with ends curved so 

 as to deflect the escaping streams into directions making angles a and /3 

 with that of the jet, the pressure on the vane in the direction of the jet 

 will be increased or diminished according as a and /3 are greater or less 

 than 90. 



As before ti = 



= t 



The final momentum per sec. in | 

 the direction of the jet j 



2 



cos 

 2 



W 

 9 



Wv* 



g 



TIV 



= v 



v cos a 



.'. Change of momentum per' sec. | 

 in this direction, by impact j 

 .*. Pressure on vane in direction of jet 



_ W 2 J 1 __ cos a + cos ft _ cos B (cos ft cos a) 



~~ g ( ^2~ T- 



This is a maximum when 

 a = 180 and ft = 180, i.e., 

 when the discharge is returned 

 parallel to the jet, and then has 



In this 



the value - - v 2 1 Ibs. 

 9 



particular case, as whenever 

 a = ft, the pressure is indepen- 

 dent of 6, the angle of impact. 



(3) Impact on a Surface of Revo- 

 lution Symmetrical with respect 

 to the Jet (Fig. 166). 



Here let a = angle of deflection of jet. 



H.A. 



f 2 cos /3 } 

 ti cos a -f t 2 cos ft } 

 t ti cos a 2 cos /3 } 



Ibs. 



FIG. 166. 



B B 



