163 



ventional pitot static tubes at each of the above 

 radial positions. 



The high Reynolds number measurements could only 

 be carried out at self-propulsion conditions. 

 However, the model experiments in the ship tank 

 were run over a range of propulsion conditions, 

 the model speed, propeller rpm, and resistance being 

 recorded. 



Analysis of Experimental Data 



The low Reynolds number results for vehicle A are 

 presented in Figures 8 and 9 while the equivalent 

 high Reynolds number trail data is given in 

 Figure 10. For body B the available data is 

 restricted to that obtained in the low Reynolds 

 number ship tank tests and the results are pre- 

 sented in Figures 11 to 13. For the sake of 

 brevity the velocity profiles given in Figures 11 

 to 13 have been limited to those for alternate 

 measurement radii. 



It can be shown that the propeller diffusion 

 ratio, defined as the ratio of the mean velocity 

 through the propeller to the unpowered mean wake 

 velocity through the propeller position, can be 

 obtained from the propeller thrust or hull resis- 

 tance together with the mean volumetric wake and 

 thrust deduction. Thus, using the model powered 

 and unpowered resistance measurements and values 



of wake and thrust deduction obtained from previous 

 model tests, the propeller diffusion ratio has been 

 calculated for the model propulsion conditions 

 pertaining during the experiments. Similar calcu- 

 lations have been carried out for the sea trial 

 conditions using data obtained from previous pro- 

 pulsion trials. The results of these analyses are 

 given on Figures 8 to 13, and also in Table 1 which 

 summarises the experimental and trial conditions. 



The velocities just ahead of the propeller have 

 been averaged at each radius to give the variation 

 of the mean circumferential velocities with diffu- 

 sion ratio presented in Figures 14 and 15. In an 

 attempt to quantify the secondary flow component in 

 the above velocity profiles the ratio of the mean 

 peak velocity to the mean minimum velocity has been 

 evaluated and plotted in Figures 16 and 17. The 

 normal parameter used to specify the velocity defect, 

 namely the ratio of the minimum velocity in the 

 'trough' to the mean velocity at the edge of the 

 'trough' is given in Figures 16 and 18. No values 

 are given for the inner radius on body B because, 

 as can be seen from Figure 11, the wake defect is 

 not clearly defined at this position. The latter 

 parameter is also compared in Figure 19 with an 

 empirical relationship based on two-dimensional 

 data [e.g. , Raj (1973) ] . 



The results of using the Myring based boundary 

 layer prediction method as described in Section 4 

 for the powered model and trial conditions are 

 also plotted in Figures 14 to 18. 



DIFFUSION RATIO 



1-226 



•I30 



0-8 l-OOO 



0-7 . 



■SELF PROPULSION. 



-UNPOWERED 



0-6 



O-S 



0-4 



20 lO O lO 20 



ANGULAR POSITION C) 



30 



FIGURE 8. Vehicle A model velocity profiles 

 at position 12.5 percent of propeller radius 

 from the hull. 



DIFFUSION RATIO 



1-308 SELF PROPULSION 



1-226 



I- ISO 



I - OOO UNPOWERED 



0-7 . 



O^ 



30 



20 10 O 10 20 

 ANGULAR POSITION W 



FIGURE 9. Vehicle A model velocity profiles 

 at position 25 percent of propeller radius 

 from the hull . 



