[farmer] determination OF COEFFICIENT OF DISCHARGE 



S3 



The coefficient has the liighest value i'or the lowest heads, ami «lim- 

 inishes as the head is increased, but the rate of diminution decreases so 

 that at very high heads the coetticient would be fairly constant at a mini- 

 nium value. In the plotted diagrams of the results it will be noted that 

 the curves are evident]}' asymptotic to a line parallel to the base along 

 which the heads are measured. 



The coefficient for orifices of the same area under the same head are 

 smaller the more closely the shape of the orifice apj)roximates to a circle. 

 Thus the square gives a smaller coefficient than the triangle or a rect- 

 angle. This includes also the conclusion expressed by Weisbach, that the 

 coefficients for rectangles increase as the rectangle becomes more elon- 

 gated. 



For orifices which are not symmetrical in every direction, the posi- 

 tion in Avhich the orifice is placed afîects the coefficient slightly. From 



Coefficient of discharge 



n» eifrcRCNT siapeo o/i/r/as. 



HEAÛ lit FtET. 



Diagr.am I. 



the results given for rectangular orifices, it appears that the coefficient is 

 greater the less the difference of head over the orifice. A curious excep- 

 tion may be noted, however, in the case of the rectangle of sides in the 

 ratio of 16 to 1, when both positions give the same coefficient for a head 

 of 14 feet, and for greater heads the position in which the long side is 

 vertical gives the greater value of coefficient. For the square orifice, the 

 position, when the diagonals are horizontal and vertical, gives a higher 

 value of the coefficient than the position in which the sides are horizontal 

 and vertical. 



A description will now be given of a series of experiments made on 

 the effect of the impact of a circular jet on diflPerent shaped vanes under 

 various conditions. The experiments were carried out by means of a 



