384 



HYDRAULICS AND ITS APPLICATIONS 



numerically equal to v 3 , and corresponds to the direct impact of two 

 streams of equal velocity. A film of water is then formed, the velocity 

 of whose mass centre (v 3 in the equation of momentum) is zero, but 

 which has a velocity of outward flow equal to ?'i or v 2 . Professor Osborne 

 Keynolds illustrated this by allowing two streams of equal velocity to 

 meet by direct impact, and noting the clear and glassy appearance of the 

 resultant film. If a cylindrical prism having plane and parallel ends bo 

 placed in the path of the stream (Fig. 174), the films from A and B to 

 the point of contact C, are still perfectly clear. After C, however, the 

 frosted appearance of the film indicates eddy formation and the institution 

 of sinuous motion. 



AET. 110A. COMPOUNDING OF CONFINED STREAMS. Loss AT IMPACT. 



When the impinging streams are confined, the pressure is no longer 

 the same before and after impact and the available data is insufficient to 

 allow the equations of momentum to be applied. Experiments by the 

 author 1 on the loss following the impact of such streams, only one of 

 which is deviated by the impact, show that this is given by 

 v 2 



loss = a 5 + b ^r- ft. Ibs. per Ib. of the impinging jet 



& (f 40 



(2) 



By the impinging jet is meant that which suffers deviation. The 

 velocity of this jet is r 2 while the velocity of the primary or undeviated 

 stream is 1-1. The values of the constants a and b depend on the angle 

 of impact 6, and on the ratio m of areas of the primary and imping ng 

 streams. The values of in the experiments were varied from 5 to 90, 

 while m was varied from 1 to 5. The area of the impinging stream was 

 y X 1" throughout, and the area of the primary stream was the same 

 before and after impact. The velocities ranged up to 23 ft. per sec. 

 Under these conditions the following are the values of a and of b. 



Proc. Roy. Soc. Edinburgh," l'J12-13. 



