Desai and Lieber 



DRAG ru iJX-!-* ,^^,vo 



The component of force exerted by the fluid on the cylinder per its unit 

 dimensional length along the polar axis in the direction of the velocity G^ is 

 given by 



. .^^ = +1/2 .2- . , . . 



F= [{ p COS d - a-^-^ COS + a-^ sin 9) t] ^ d9 dz . (1.89) 



Since 



where 



and 



and where 



. 1 .2 ~ - -^2 



z = za , P = - pu^p + p„ , o--- = pu^cr^^ 



2 3u_ 



he = P^^'^tO 



1 / 1 du Bv V 

 R^ U 3? ^ b7 r 



the right-hand side of Eq. (1.67) can be rewritten: , , ; 



F = pu^a^ I / — p cos 9 - a ^^ cos 9 + a^g sin 9\ 69 , 

 "^ -0 \ 2 /r=l 



using 



277 ~ 



J„ n,,2 



COS0d0 = 



The projected area per unit length of the cylinder is given by 



Area ~ (2a) x a = 23^ . 



Hence the drag coefficient defined by c^ = F/[l/2(pu2)] x projected area 

 is given by 



/277 

 (- p cos9 - a^^cos9 + a^gsind) dd = C^(Re) . (1.90) 



^2 /r=i 



554 



