94 



FIGURE 16. Random photographs of the flow past the 

 Schiebe body at a Reynolds number of 3.4 x 10^ with 

 background turbulence level of 1.1 percent. The 

 region shown covers the arc length diameter ratio of 

 0.68 to 0.93. 



HEMISPHERE NOSE BODY 



1- 



D 



-I 



A 

 • 



tr 

 g 

 OT 0,80 



O 



CL 



ESTIMATED SEPARATION 

 LOCATION (THWAITES METHOD) 



NSRDC BODY 



s 



■"*■ 

 ▲ 



TURBULENCE 

 • 0.05°/ 

 ■ 065'/, 

 A I.I0°/1 

 O 2.30°/l 

 D 3.60°/ 



15x10^ 



2,5x10^ 35x10* 

 BODY REYNOLDS NUMBER- UD/i/ 



FIGURE 18. Observed separation locations as a func- 

 tion of turbulence level for two bodies. 



negative. Note that the position of transition on 

 the free shear layer coincides with the definition 

 of the end of the separated bubble. 



Each of these measured quantities was non- 

 dimensionalized by dividing by the body diameter 

 and are plotted versus the body Reynolds number 

 with the freestream turbulence level as a parameter 

 in Figures 18 through 21. For the NSRDC body, Fig- 

 ure 19 shows that the size of the separation bubble 

 decreases with increasing velocity and turbulence 

 level — the critical Reynolds number being reduced 

 from a value of greater than 4 x 10^ at 0.05 per- 

 cent to near 2.5 x 10 at 3.6 percent. As was ex- 

 pected from the schlieren photographs of the 

 hemisphere nose (Figure 14) , Figure 20 shows the 

 length of the separation bubble is independent 

 of turbulence level but decreases with increasing 

 velocity. Finally, Figure 21 shows that as with 

 the NSRDC body, the position of transition on the 

 Schiebe body moves forward with increasing velocity 

 and turbulence intensity. 



The most startling result of the above tests was 

 the insensitivity of the boundary layer on the 

 hemisphere nose to the present disturbances imposed 

 by the freestream turbulence. Hall and Gibbings 



(a) POSITION OF LAMINAR SEPARATION OR 

 TRANSITION WHICHEVER IS APPLICABLE 



(b) LENGTH AND HEIGHT OF SEPARATED REGION 



FIGURE 17. Definition sketch of separation location. 



1.5X10^ 



2.5X10^ 3.5x10= 



BODY REYNOLDS NUMBER-UDA 



FIGURE 19. The length of the separated region as a 

 function of freestream turbulence level for the 

 NSRDC body. 



