FORCES OF OBLIQUE WINDS ON TELEPHONE WIRES 593 

 TABLE \\— {Continued) 



In characterizing the normal force of oblique winds, curves were 

 plotted between the normal force (F„) and the angle {a) between the 

 wind and the normal to the wires. Figures 3 (0.104-inch wire) and 

 4 (0.165-inch wire) show these curves. 



In studying the significance of these curves and the underlying data, 

 consideration was first given to the extent to which the case of normal 

 winds (cos a — \) followed the law of dynamic similarity. This law 

 states, in effect, that for any two geometrically similar bodies moving 

 through a fluid, 



(5) 



F=pV'f 



(") 



Here, Fis the unit force at either of two similarly situated points on the 

 two bodies, p is the fluid density, V is the velocity of the body, D a 

 linear quantity depending on the dimensions of the body and v is the 

 kinematic viscosity of the fluid. The function (VD/v) is the well 

 known Reynolds number and the key to dynamic similarity require- 

 ments in model experiments made at ordinary velocities. The 

 principle of dynamic similarity is satisfied as long as the Reynolds 

 number is held constant. 



In Report No. 102 ^ of the National Physical Laboratories is given an 



* Reports and Memoranda No. 102, November 1914, entitled "Discussion of the 

 Results of Measurements of the Resistance of Wires" by E. F. Relf. 



