A • TRANSITION FROM LAMINAR TO TURBULENT FLOW 



value of (Tw - T,)/Tl of 0.14 reduced the transition Reynolds number 

 to values of about 3 million. In order to study the effect of cooling, it was 

 necessary to add artificial roughness in the form of grooves to move tran- 

 sition forward. Under these conditions the transition Reynolds number 

 was about 2 milHon. Cooling to a value of {T^ - Tr)/Tl of -0.065 at a 

 Mach number of 2 increased Re^ to 3.4 milhon and cooHng to —0.10 at a 

 Mach number of 1.5 to 3.8 million. 



Eber [119] found that heating to a wall temperature 125°F above the 

 recovery temperature on a cone cylinder model (40° cone) in the Naval 

 Ordnance Laboratory 40-cm wind tunnel at a Mach number of 2.87 de- 

 creased the transition Reynolds number from 300,000 to 160,000 whereas 

 coohng by 50°F increased it to 450,000. 



H 



H^ 





Fig. A,26c. Comparison of experimental results on stabilization 

 by cooling with the Dunn and Lin theoretical curve. 



Czarnecki and Sinclair [111] made measurements on the RM-10 body 

 of revolution at a Mach number of 1.61 in the NACA Langley 4-foot 

 wind tunnel for which the transition Reynolds number of the insulated 

 body is 11.5 milHon. Heating to a value of (Tw - T,)/Tl of 0.3 reduced 

 the transition Reynolds number to 3 milhon; coohng to {T^ — T^)/Tl 

 equal to —0.15 increased it to 28.5 milhon. Roughening the surface by a 

 cellophane tape at 3 and 25 per cent of the body length reduced the value 

 from 11.5 to 5 and 7.5 milhon, respectively, and these values could not be 

 increased by coohng the roughened body to (Tw — T^) equal to —0.15. 



Jedlicka, Wilkins, and Seiff [94] investigated transition on small 

 models fired from a 50 caliber smooth-bore gun at 4000 feet per second 

 with the aid of a plastic sabot. While the principal object of the investi- 

 gation was to study roughness effect, the short flight times mean that 



< 66) 



