TABLES 339-346A.— AERONAUTICS * 337 



TABLE 339.— DYNAMIC PRESSURE AT DIFFERENT AIR SPEEDS 



The force on a body moving through a fluid may be expressed in the form 



F= Cf q A 



where F is the force, CV a nondimensional force coefficient, q the dynamic pressure (q = 

 $pV 2 , definition), and A an area. In general, the value of the coefficient Cf is dependent 

 on several nondimensional parameters. When the medium is air, Cf depends on the 



yip V 



Reynolds number — -, the Mach number — > the body shape and attitude to the relative 

 i) a 



wind, the relative surface roughness, and the degree of turbulence of the air stream. The 

 quantity p denotes the fluid density, V the velocity of the body relative to the fluid, tj the 

 coefficient of fluid viscosity, / a linear dimension of the body fixing the scale, and a the 

 speed of sound in the ambient fluid. 



The table gives values of dynamic pressure q for a wide range of speeds. In conjunction 

 with the values of the force coefficient in subsequent tables, this table can be used for 

 computation of lift, drag, and moment under specified conditions. The values in the table 

 are computed for standard air density: dry air, normal C0 2 content, 15°C, one atmos- 

 phere. Standard air density is 0.12497 j — — or 0.002378 , f For standard gravity, 



m it 



the weight of one metric slug (MKS) is 9.807 kilograms and the weight of one slug is 

 32.174 pounds. For other densities the values must be multiplied by the ratio of the actual 

 density to the standard density. 



* Tables 339 to 346 and figures 6 to 15 were prepared under the direction of C. H. Helms, assistant 

 director of aeronautical research, National Advisory Committee for Aeronautics. 



(continued) 



SMITHSONIAN PHYSICAL TABLES 



