A • TRANSITION FROM LAMINAR TO TURBULENT FLOW 



the body Reynolds number Vc/v, plot curves of Re^* vs. s/c' for several 

 values of Re as in Fig. A,12f and A,12g. On the same diagram plot 

 {Res*)cT vs. s/c' as computed in 3. 



For each value of Re determine the intersection of the Re^* curve with 

 the {Res*)cT curve and read the value of s/c' which is the location of 

 transition for this Reynolds number. Plot the values of (s/^Ocr vs. Re 

 to give the transition position as a function of Re as shown in Fig. 

 A,12h and A,12i. 



10^ 



\ V / cr 



103. 



8 

 6 



4 



102 



0.1 



0.2 0.3 



s/c' 



0.4 



0.5 



Fig. A,12g. Variation of displacement-thickness Reynolds number for Joukowsky 

 I airfoil as function of airfoil Reynolds number and local position. 



Schlichting had no reliable data in air streams of low turbulence to 

 compare with his theoretical computations. The method as outlined is 

 capable of considerable improvement, since the approximate methods 

 used both for the stability calculations and the boundary layer thickness 

 calculations are relatively crude. Furthermore it is desirable to use the 

 experimental pressure distribution, if available, rather than that com- 

 puted on potential flow theory. The most serious criticism, however, is 

 that we know definitely that transition does not occur at the critical 

 Reynolds number for instability of the laminar boundary layer but at a 

 considerably higher Reynolds number, and no method is known for com- 

 puting the ratio of the two. Hence the method as described cannot be 

 expected to give valid results. 



< 36) 



