Table 1 60 

 FORCES ON THIN FLAT PLATES AT ANGLES TO THE WIND 



[99 



For plates at angles, the force is usually resolved into components at right angles and 

 parallel to the direction of the relative wind. The components, termed the lift and drag 

 respectively, are expressed in the form of absolute coefficients, the forces being divided by 

 the product of the velocity pressure and the area of the plate (N. B. — not the projected 

 area on a plane normal to the wind). The line of action of the force is given by the inter- 

 section of the resultant force with the plate expressed as the ratio of the distance of the 

 intersection from the leading edge to the chord length, a quantity called the center of 

 pressure coefficient. The lift coefficient L = Y\ft/Aq, the drag coefficient D = drag/ Aq, and 

 the center of pressure coefficient for various angles are given for plates of aspect ratios I, 3, 

 and 6 in the form of graphs. (See page 198.) 



The following formulae indicate the use of the coefficients from the plots for the deter- 

 mination of the forces: 



Fd = component of resulting wind force parallel to wind = drag = DAq; 

 Ft = that normal to wind and width = lift = LAq; 



x c (see small figure in upper set of curves) = CP • W; W is that dimension of the plane of 

 reference which makes the least angle with wind. 



A = area of one surface of plate. D, L, CP are independent of Reynold's No. and tempera- 

 ture. 



Authorities and the conditions of their experiments: (i) Eiffel. (2) Dines, 1890. (3) Foppl, 1010. (4) Ria- 

 bouchinski, 1912. (5) Stanton, 1903. (6) Bureau of Standards. In lower figure of previous page: L\. Foppl; 

 Li. Li, B. of S.; Li, Eiffel; D\, Foppl, B. of S.; Di, B. of S.; D3, Eiffel. For more detailed information as to 

 references and data see I.C.T. 1, 406, 1926. 



Smithsonian Tables 



