91 



INJECTOR 



9:1 CONTRACTION 



SINTERED BRASS 

 DISC 



'//////^ 





WZZZZ^^s^ 



■HOLES FOR 

 CARTRIDGE HEATERS 



SMOOTHING SECTION- 

 PACKED WITH POROUS FOAM 



FIGURE 9. Cross-section of injector used for these 

 polymer experiments. The body diameter is 5 cm. 



Meulen's (1973) example and inject the polymer into 

 the boundary layer through a hole at the stagnation 

 point. To do this an injector was designed to in- 

 troduce the polymer into the boundary layer without 

 also introducing disturbances. The injector is 

 shown schematically in Figure 9 assembled inside 

 the hemisphere nose body and consists of first a 

 settling chamber 12.7ram in diameter and 31.75mm long. 

 This section was packed with porous plastic foam 

 held in place by a sintered brass disc. The pur- 

 pose of this section is to disperse the jet enter- 

 ing the injector and provide a smooth flow into the 

 9:1 contraction which follows. After the smooth 

 contraction there is a tube with a length to diam- 

 eter ratio of 22 and this tube ends at the surface 

 of the model. 



To minimize polymer degradation, the polymer 

 solutions were "pushed" through the injector from a 

 reservoir by using compressed air instead of a pump. 

 A check with a turbulent flow rheometer [the same 

 one as used by Debrule (1972) ] showed degradation 

 of the polymer after it passed through the injec- 

 tion system to be minimal. Preliminary tests were 

 carried out with water as the injectant to ensure 

 that the injection process itself was not respon- 

 sible for any observed changes in the flow. Results 

 of these tests for the NSRDC body are presented in 

 Figure 10 and show that even at an injection rate 

 of three to ten times higher than actually used 

 with polymer solutions no differences are detectable 

 from the no-injection case. 



Nuclei Counter 



Nuclei distributions were deduced from holograms 

 of the test fluid. The experimental apparatus and 

 method is much the same as used by Peterson (1972) , 

 Feldberg and Shlemenson (1973) and is described in 

 detail in Gates and Bacon (1978) . Essentially it 

 is a two-step image forming process. In the first 

 step, a hologram of a sample volume of the water 

 in the tunnel test section is recorded on a special 

 high resolution film by a "holocamera. " In the 

 second step, the developed hologram is reconstructed 

 producing a three dimensional image of the original 

 volume which can be probed at the investigator's 

 leisure. The holocamera and reconstruction system 

 are shown schematically in Figure 11 and 12 respec- 

 tively. 



FIGURE 10. Schlieren photographs showing the effect 

 of injecting water on the NSRDC body at a body Reynolds 

 number of 3.2 >■ 10^, (a) injection rate = m£/sec , 



(b) 1.8 mJl/sec, (c) 3.6 mH/sec, (d) 6.6 mJl/sec, 



(e) 9.8 m£/sec. No effect is observed. 



1 — 30cm 



SAMPLE VOLUME 



CS 



TEST SECTIO N 

 WINDOWS 



AB C 



EF G H I J 



P= 



:4^^aE^ 



MODEL 



-FLOW 



-60 cm 



Qm 



FIGURE 11. Diagram of the holocamera; (a) dielectric 



mirror, (b) iris, (c) dye-quench cell, (d) ruby-flash 



lamp assembly, (e) iris, (f) dielectric mirror, 



(g) beam splitter, (h) neutral density filter, 



(i) beam expander lens, (j) 25p pinhole, (k) collimat- 



ing lens, (1) front surface mirror, (m) p.i.n. diode, 



(n) film pack . 



