252 MOTION OF AIR IN LONG PIPES. 



He found that the coefficient of friction, when the velocity was given 

 in feet, could be expressed approximately by the following formula, 



The resistance caused by elbows and bends is to be treated in the 

 same way as in the case of water (Arts. 110, 111). 



134. Motion of Air in Long Pipes. By the aid of 

 the coefficient of friction of a pipe, we can calculate the 

 velocity of efflux and the discharge for a given length and 

 diameter of the pipe. 



Let v = the velocity of discharge = - 



ic 



Vi = the velocity of the air in the pipe. 

 d = the diameter of the orifice, whose area there- 



fore is k = ^d?. 

 d l = the diameter of the pipe. 

 )3 = the coefficient of resistance at the entrance to 



the pipe. 

 / = the coefficient of resistance due to the friction 



of the pipe. 



j3 x = the coefficient of resistance at the orifice. 

 p l = the pressure of the air when it is discharged. 

 w = the weight of a cubic foot of air. 

 h = the height of the manometer in the reservoir. 

 b = the height of the barometer. 

 I = the length of the pipe. 



Then the height due to the resistance at the entrance to 

 the pipe, 



The height due to the resistance of friction in the pipe 



