40 



Ribbon at X = 3.75 inches 



T„-T„ = 0° F A = 0.656 inches 



ui^ X 10^= 138 



O X = 4.0 in. 



D X = 4.5 in. 



* X = 5.0 in. 



O X = 5.5 in. 



Solution bv Lowell, Rg • = 601 



(x = 5.5 in.) 



— Lowell solution Rj. =890 



T„-T„=5°Fuj, X106 = 81 

 O Data for T^^-T^ = 5.2° F 

 uj, X 10^ = 83 Re. =890 



FIGURE 7. Velocity and temperattire fluctua- 

 tion aitiplitudes in the boundary layer. 



-- 



Neutral Stability - For reference, the neutral 

 stability results for the unheated plate will be 

 presented first. Neutral points obtained in the 

 present experiment are plotted together with those 

 from prior investigations in Figure 9. The solid 

 line in Figure 9 is the non-parallel flow solution 

 of Saric and Nayfeh (1975) while the dashed line 

 is the corresponding parallel flow solution of 

 the Orr-Sommerfeld equation. Lower branch neutral 

 points in the region Rg* < 500, m^ < 210 x 10"^ are 



X 



< 



I 

 I- 



O 



CO 



a 



a: 



I- 



denoted by bars in the present work because dis- 

 tinct neutral points could not be identified. Ex- 

 perimental results indicate that a neutral point 

 lies somewhere in the barred region at each dis- 

 turbance frequency considered. The present re- 

 sults are in agreement with the experimental 

 results of Ross et al. (1970) , Schubauer and 



X 



3" 





a 



o 



U5 



OCD 

 D 



Theory 



Non-paratlel flow solution (Ref. 7) 

 Parallel flow solution (Ref. 12) 



Data 



Present investigation 

 Schubauer and Skramstad (Ref. 1 ) 

 Rosset al. (Ref. 21 

 Wortmann (Ref. 31 



FIGURE 8. Measured disturbance growth characteristics 



for vmiform wall temperature distributions. Re,.. = 800. 



o 



420 



360 



300' 



240 



180 



120' 



60 



o4-/ — I > 1 ' ' 



400 600 800 1000 1200 

 DISPLACfMENT THICKNESS REYNOLDS NUMBER, Reg. 



FIGURE 9. Neutral stability results for the unheated 

 plate. (Solid symbols denote lower branch points, 

 open symbols denote upper branch points) . 



