[farmer] determination OE COEFFICIENT OF DISCHARGE 



61 



From the Table of Coefficients of Impact it is evident that under the 

 conditions which obtained in these experiments, theory gives a very 

 incorrect value of the actual force. 



Diagrams have been drawn only for particular series, but the facts 

 brought out b}^ them are borne out by the results generally. 



Diagram VI, is plotted to show the variation of the coefficient with 

 the angle through which the stream is deflected. The coefficients raj^idly 

 diminish as the angle of deflection increases. The diagram also indicates 

 the interesting fact that, whereas with small deflections the parabolic arc 

 gives the greatest coefficient, followed by the elliptic and the circular, 

 when the deflections become larger this order is reversed. 



Diagrams VII. and VIII. illustrate the variation of the coefficient 

 with the velocity for a vane of each pattern, giving approximately the 



ANCL£ ABOUT 4-5 



Diagram VII. 



Diagram VIII. 



same angle of deflection. Two cases are given ; in Diagram VII. the 

 angle of deflection is about 43° more than a right angle ; in Diagram 

 VIII. it is about 62° more than a right angle. A fall in the value of the 

 coefficients is noticeable as the velocity decreases. In the case of the 

 vanes of circular and elliptic sections with the deflection of 42° there 

 appears to be a maximum value of the coefficient for a velocity of about 

 30 feet per second. 



