165 



DIFFUSION RATIO 



1233 SELF PROPULSION 



1-175 



l-ll I 



•O i-OOO UNPOWERED 



o-e 



-I 0-7 



w 



a 

 o 



3 



0-6 



CONTROL 

 SURFACE 



50 



40 



20 lO O lO 20 

 ANGULAR POSITION (°J 



FIGURE 13. Vehicle B model velocity pro- 

 files at position 54.5 percent of propeller 

 radius from the hull. 



surprising since the two radii concerned are close 

 to the hull and the velocity defect is developing 

 in a complex three-dimensional flow field influenced 

 by the secondary flow and this is possibly leading 

 to a more rapid mixing of the flow. The results 

 obtained over a much larger distance from the hull 

 on vehicle B support the above hypothesis since it 

 can be seen from Figures 18 and 19 that as the 

 distance from the hull increases the magnitude of 

 the wake defect increases and approaches the two- 

 dimensional value. The model results for vehicle 

 B shown in Figure 18 tend, in general, to indicate 

 a small increase in the depth of the wake defect 

 as the propeller diffusion ratio increases. The 

 maximum value of this increase in the wake defect, 

 between the model self-propelled and unpowered 

 condition, is only of the order of 3 percent. This 

 change is somewhat surprising since the propeller 

 produces a favourable pressure gradient aft of the 

 control surfaces, and on the evidence of two- 

 dimensional data this would be expected to reduce 

 the wake defect. 



FULL SCALE MEASUREMENTS. 

 -)- MODEL EXPERIMENTS. 



0-8 



o/e PROPELLER 

 RADIUS FROM 

 HULL 



0-7 . 



0-6 



0-5 



0-4 



FULL SCALE 

 UNPOWERED PROPULSION 



J I I I 



FULL SCALE PREDICTIONS 



MODEL 

 PREDICTIONS 



0\—\- 



MODEL SELF 

 PROPULSION 



Jl I I 



l-O l-l 1-2 1-3 1-4 

 PROPELLER DIFFUSION RATIO- 



In contrast to the velocity defect the secondary 

 flow can be seen from Figures 16 and 17 to be 

 significantly reduced by the presence of the 

 propeller, this reduction becoming larger as the 

 diffusion ratio increases. Additionally, at equal 

 propeller diffusion ratio, the full-scale secondary 

 flow is significantly less than measured on the 

 model. From the data obtained on vehicle A 

 (Figures 14 and 16) it can be seen that, comparing 

 the results at model and full-scale self-propulsion 

 conditions, the magnitude of the secondary flow and 

 the mean circumferential velocity at the two radii 

 considered agree to within 2 percent and 3 percent 

 respectively. Although comparison between the 

 velocity profiles is difficult because of the non- 

 symmetry of the trial data. Figures 1 to 3 indicate 

 that at these conditions there is also reasonable 

 agreement between the velocity profiles. These 

 results indicate a possible condition for similar 



l-O 



> 0-9 

 O 



o 



> 



ul 



O 0-7 



X 

 u) 



> 



J 0-6 



UI 



Q 



o 



2 



« O-S 



o 



-1 



3 



0-4 



0-3 



7o PROPELLER 

 RADIUS 

 FROM HULL 



6S■0^^ ^ 



54-5<^ '^ 



44-O-K "^ 



33-5< 



23- O*' 



12-5-K' 



/ 



^+ 



+ MODEL EXPERIMENTS 



'' PREDICTIONS 



UNPOWERED 



-^ \ L- 



MODEL SELF 

 PROPULSION 



I I u_ 



l-O II 1-2 1-3 

 PROPELLER DIFFUSION RATIO 



FIGURE 14. Mean circumferential velocity in the measur- 

 ing plane for vehicle h. 



FIGURE 15. Mean circumferential velocity in the mea- 

 suring plane for vehicle B. 



