200 



Table 161 

 FORCES ON NON-ROTATING CIRCULAR CYLINDERS 



The coefficient for cylinders normal to the wind, the area A being taken as the product 

 of length and diameter and the linear dimension L as the diameter, depends to a marked 

 degree on the ratio of length to diameter and on the Reynolds Number, R. The graph 

 shows the variation of C with R for cylinders of infinite length. 



The variation of C with the length-diameter ratio for a Reynolds Number of 80,000 is 

 as follows : 



If the axis of the cylinder is inclined to the wind direction, the force remains approxi- 

 mately at right angles to the axis of the cylinder, its magnitude falling off approximately 

 as the square of the sine of the angle of the axis to the wind. 



Air Forces, Circular Cylinders. 



Force = CAq. Reynold's number = R = VDp/fi. 



C is taken from above plot ; for q see Table 157 ; A— Area axial section of cylinder = 

 L (length) X D (diameter) ; the plane of reference contains the axis and is perpendicular 

 to the plane defined by the axis and the wind direction ; V = air speed ; ?, the density of 

 the medium and fi, its viscosity. Curve (a) is due to Wieselsberger, 1922; curve (b) 

 to Relf. 

 Smithsonian Tables 



