344 



TABLE 341A.— SKIN FRICTION ON FLAT PLATES (FIGS. 11, 12) (continued) 

 .0 10 



.006 

 .004 



.002 

 F 

 .00 1 



.000 6 

 .000 4 



.0002 



.5 1.0 2.0 5.0 



REYNOLDS NUMBER, R 



20XI0 6 



Fig. 11.— A log-log plot of the skin-friction coefficient C f on a flat plate as a function of 

 the Reynolds number for laminar and turbulent flow. 



The local skin-friction coefficient-^ may be approximated by a power function of the 



Reynolds number based on the momentum thickness, Re = — — . When the boundary 



layer is laminar 



I±= °- 2205 

 2<7 Re 



When the boundary layer is turbulent 



To _ 1 , 



2<7 



[ 



2.5 log 



The momentum thickness 



2.5(1— 5Vro/2</) 



+ 5.5 



where u is the local velocity inside the boundary layer, V the local velocity outside the 

 boundary layer, and 5 the boundary-layer thickness. The local skin-friction coefficient is 

 plotted against Reynolds number for the case of a turbulent boundary layer. 



{continued) 



SMITHSONIAN PHYSICAL TABLES 



