NO. 4 



WIND TUNNEL EXPERIMENTS IN AERODYNAMICS 



85 



that the viscous drag is important. An entirely different form of 

 flow may then exist, and the resistance should no longer vary as the 

 square of the velocity. The change from turbulence to steady flow 

 should be marked by a critical velocity. The resistance of disks, aero- 



Fig. 36. 



plane wings, and all sharp-edged objects is usually represented by a 

 formula as follows : 



where 



R = KpAV'', 



R is resistance in pounds, 

 p is density in pounds per cubic foot, 

 A is area in square inches, 

 V is velocity in miles per hour, 

 K a coefificient assumed constant. 



