F • CONVECTIVE HEAT TRANSFER IN GASES 



should promote, and cooling retard, transition. That this is the case has 

 been shown experimentally by Scherrer [51], Higgins and Pappas [52], 

 and Czarnecki and Sinclair [53] of the National Advisory Committee for 

 Aeronautics, Eber [54] of the Naval Ordnance Laboratory, and van Driest 

 and Boison [55,56] of North American Aviation, Inc. Plate F,17 is a set of 

 photographs by van Driest and Boison showing the boundary layer when 



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C 



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Complel-e stobility 

 (2-dimensionaI 

 disturbances) 



y_ 



Fig. 



1.0 1.4 1.8 2.2 2.6 3.0 3.4 



Average wall-to-Iocal^tream temperature ratio 



Tw/Te 



F,17c. Effect of surface cooling on transition Reynolds number for 

 several local Mach numbers on a smooth 10° cone. 



it is distorted (magnified) 20 times normal to the flow by means of a cylin- 

 drical lens built into the Schlieren system [57]. Transition and its delay by 

 cooling is readily discernible from the photographs. The length of each 

 photograph represents 16 inches of a smooth 10° (apex angle) cone, cooled 

 internally with gaseous nitrogen; the left-hand edge of each photograph 

 is located 4.5 inches from the apex of the cone. The Reynolds number 

 per inch is 500,000. The effect of surface cooling [56] on the transition 

 Reynolds number for several local Mach numbers on the cone in a low 

 turbulence tunnel is indicated in Fig. F,17c. Lines of infinite minimum 

 critical Reynolds number are also plotted in the figure. The dashed line 



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