89 



ELLIPSE 



R--D/2 



D/6 



D/2 



-A- 



body diameters upstream of the sting in each case. 

 Misalignment from the geometric tunnel center-line 

 in both the LTWT and HSWT was measured to be about 

 0.2°. 



HEMISPHERE NOSE NSRDC BODY SCHIEBE BODY 



Cp„i„ = -0.75 

 (BRASS) (COPPER) (CRESl 



FIGURE 3. Definition of test models. 



2. EXPERIMENTAL EQUIPMENT AND METHODS 



Test Models 



Three axisymmetric test models were used in the 

 present experiments: a brass hemisphere nose, a 

 copper modified ellipsoidal (or NSRDC) body, and a 

 stainless steel standard headform from the Schiebe 

 series with a minimum pressure coefficient (Cpmin) 

 of -0.75. The hemisphere nose and Schiebe bodies 

 were fabricated specifically for these tests, 

 whereas the NSRDC body is the same as that used 

 by Brockett (1972) and Arakeri (1976) . Each body 

 is 5.08 cm in diameter and has a 0.423 cm diameter 

 hole at the stagnation point for polymer injection. 

 No quantitative measure of surface roughness was 

 made, but each model was highly polished [a highly 

 polished surface typically has a 0.1 x 10"7m rms 

 finish, Beckwith and Buck (1961) ] . The model ge- 

 ometries are shown in Figure 3. 



The models were supported by a two-bladed sting 

 in the LTWT and by a three-bladed sting in the 

 HSWT with the nose of the model being about six 



SPARK-GAP LIGHT SOURCE (0.032 DIA.) 

 SLIT, GATHERING LENS F.L.= 3 ' 



REMOVABLE 

 MIRROR 



|r.-^-=i-_-r_':ifY'~o STEADY LIGHT SOURCE 



3^0LLIMAT1NG LENS 

 F.L. = 12", /2.5 



-WINDOWS (FLAT OR WITH 



CORRECTOR LENS) 



TUNNEL TEST SECTION 

 WITH HEATED BODY IN PLACE 



-FOCUSING LENS 

 F.L. = 7", /2.5 



CUT - OFF PLATE 



FILM PLATE 



Flow Visualization 



Thermal boundary layers in the viscous flow past 

 the test model were observed by schlieren photog- 

 raphy. The particular schlieren configuation used 

 is shown schematically in Figure 4 and is essen- 

 tially the same as that used by Arakeri (1973) . 

 Also following Arakeri, the prerequisite density 

 gradient was produced by heating the body with in- 

 ternal cartridge type electric heaters. An example 

 schlieren photograph obtained using this system is 

 presented in Figure 5. 



Water Tunnel 



The two facilities used in the present experiments 

 were the High Speed Water Tunnel (HSWT) and the 



FIGURE 4. Schematic diagram of flow visualization 

 system. 



FIGURE 5. A schlieren photograph of a 5 cm diameter 

 hemisphere showing laminar separation and turbulent 

 reattachment at a body Reynolds number of 2.5 ^ 10 . 

 The maximum height of the separated region is about 

 2 mm. 



