151 



Tables 138-139. 



AERODYNAMICS. 



TABLE 138. — Air Pressures upon Large Square Normal Planes at Different Speeds 



through the Air. 



The resistance F of a body of fixed shape and presentation moving through a fluid may be written 



F = pUVYiLV/p) 



in which p denotes the fluid density, v the kinematic viscosity, L a linear dimension of the body, V the speed of trans- 

 lation. In general / is not constant, even for constant conditions of the fluid, but is practically so for normal impact 

 on a plane of fixed size. In the following, p is taken as 1.230 g/l (.0768 Ibs./ft'). 



The mean pressure on thin square plates of i.i m^ (12 ft^), or over, moving normally through air of standard density 

 at ordinary.' transportation speeds may be written P =.00601)^ for i* in kg per m- and v in km per hour, or P = .0032ii2 

 for P in lbs. per ft- and 11 in miles per hour. The following values are computed from this formula. For smaUer areas 

 the correction factors as given in the succeeding table (Table 139) derived from e.\periments made at the British National 

 Physical Laborator>', may be applied. 



Unit:: the first of each group of three columns gives the velocity; the second, the corresponding pressure in kg/m^ 

 when the first column is taken as km per hour; the third in pds/ft- when in miles per hour. 



TABLE 139. — Correction Factor for Small Square Normal Planes. 



The values of Table 138 are to be multiplied by the following factors when the area of the surface is less than about 

 I m2 (12 ft2). 



Smithsonian Tables. 



