130 



HYDRAULICS AND ITS APPLICATIONS 



As is clear from the expression assumed above for the value of C, this 

 is not a constant, 6ut varies both with the depth of the water and with 

 the dimensions of the orifice, and can only be determined by experiment. 



AVith sharp-edged orifices, and a free discharge into air, the values of 

 C for a square opening are very approximately as given below (Hamilton 

 Smith). 



For vertical rectangular orifices the value of C varies with the ratio of 

 the width b to the depth d. 



The following table gives the value of the coefficient for orifices 1 foot 

 wide : 



Head in feet 



Values of d in feet. 



AKT. 50. : FLOW THROUGH A CIRCULAR ORIFICE. 



Let H = depth of centre of orifice (Fig. 71). 

 R = radius of orifice. 

 r vena contracts. 



