F • CONVECTIVE HEAT TRANSFER IN GASES 



That the theory for turbulent flow follows the data quite satisfactorily 

 is shown in Fig. F,20i. Perhaps the shght deviation after 45 sec is caused 

 by the strong stabilization effect of cooling in spite of the boundary 

 layer trip. 



Fig. F,20h is generally interesting because it shows clearly the course 

 of events which is typical of boundary layer development as a function of 



1.35 



1.30 



1.25 



1.20 



I- 



10 



40 



50 



20 30 



Time, seconds after take-off 



60 



1.15 



1.10 



1.05 



1.00 



Fig. F,20k. Variation of flow parameters on nose 

 cone of V-2 rocket in Fig. F,20h and F,20i. 



Reynolds number and wall-to-free stream temperature ratio (heat trans- 

 fer). At first, the Reynolds number soon becomes large enough to make 

 the boundary layer turbulent; therefore the data follow the turbulent 

 trend for a while. However, as the speed increases, the boundary layer 

 temperature increases, thus bringing about heat flow into the missile skin 

 owing to heat capacity of the skin. The boundary layer cooling then tends 

 to stabilize the layer; in fact, a rate of cooling is finally reached after 

 which a laminar boundary layer is stable for any Reynolds number. The 

 transition from turbulent to laminar flow is clearly seen in Fig. F,20h. 



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