23 



dx 



+ ( 





[72] 



The coefficient of local skin friction for flat plates ( Tj^ / p^^) q decreases slowly 

 with local Reynolds number Rq. A suitable formula valid lac a large range of Reynolds nuni" 

 bers is that derived in Reference 38 from the Karman-Schoenherr formula for the total drag of 

 flat plates, 





0.01466 



iogloCSff^) 



[73] 



-^\og^^[2RQ) +0.4343 



which is plotted in Figure 6. 



t 3 























































































































































































































































































































































































































































































































































































































































































( '■=) - 



0.01466 



- 





































, , P 1 , . ^ 





































^/)U 'o io9|ol'^"e' LT '°9,oVi:«e; f u.totaj 





































p-) = 



0.006361 



(Least -Squares Fit, lo'< Rg< 10® ) 











~~~" 



^^ 





— 





^ 

















„ 0.1686 

































~ 



-= 



^^==- 



=^ 



■^ 



u:= 



-. 



_. 

























































































■^ 



=.sj 



^. 



















































































^—^ 





_ 



















































































■ 





— 1 



_ 



^ 

























































































~ 





=1 



























































































































































-J 



- 





- 

























































































































































































































































































































































































































































































































































































1 1 



1 

 1 

































































r,^ 1 



5 



? 





3 





* 





5 



6 



7 ( 



3 



\ 



^* 1 



5 







3 





* 



5 



6 



r s 



i 



V 



s- ' 



b 







5 





t 







t 





' t 



^ 



\( 



l" 



Rg Boundary -Layer Reynolds Number 



Figure 6 - Local Skin Friction for Flat Plates as Function of Boundary-Layer 



Reynolds Number Rq 



A rapid procedure (and one sufficiently accurate for drag calculations) is to 

 approximate {'''„, ^ p^^)n with a power law and to assume H constant. With 



\pU / ft"* 



[74] 



