F,17 • STABILITY OF THE LAMINAR BOUNDARY LAYER 



0.75 and the viscosity is proportional to the temperature. The condition 

 (variable Pr (see Fig. F,5a), Sutherland law, T^ = 400°R) would best be 

 used for slender bodies and thin surfaces in free flight. The condition 

 (Pr = 0.715, p|m* = 1) is appHcable to cones or blunt bodies where the 



23456789 



Free stream Mach number Me 



11 12 



Fig. F,l7a. Minimum critical Reynolds number as a function of free stream Mach 

 number and wall-to-free stream temperature ratio. Prandtl number 0.75 and Suther- 

 land viscosity law. 



H 



E 



(Ur- 



CO 4- 



0) "- 

 J- (U 



M- JI 

 I -t 



"a ^ 



It 



"^7 



Inviscid solution 



Viscous solution 



3 4 5 6 7 8 9 



Free stream Mach number Me 



10 



Fig. F,17b. Cooling required for complete stabilization 

 of the laminar boundary layer for air. 



ambient temperature (just outside the boundary layer) is great so that 

 Pr = 0.715 and ju^ = T|. The calculations resulting in the above curves 

 were based on analyses of the boundary layer as given in [1,2,3]. 



Since transition from a laminar to a turbulent boundary layer is a 

 consequence of instability of the laminar flow, heating the boundary layer 



<|397 ) 



