237 



0.963 RAD 



1 -Z 



1 .1 



1 .0 



0.9 



\ 0.8 

 X 



0.7 

 0.6 

 O.S 

 O.i 

 0.3 

 0.2 

 0.1 



:> 

 -0.1 



-0.2 



0.2 

 0.1 



-0.1 

 -0.2 



20 20 40 63 80 



!20 140 ISO 182 20C 220 240 250 290 300 320 340 350 380 



RNGLF. IN DE.CRFE.S 



FIGURE 18. Velocity component 

 ratios for R/V ATHENA and DTNSRDC 

 model 5365 at 0.963 radius. 



3 10 



Velocity Profile Data From R/V ATHENA 

 and Wind Tunnel Model 5366 

 Location I, x/L^i_ = 0.90 



O RUN 209 U. = 3 2 m/s, R^ = 1.74 xio' 



D RUN 210 U, = <>,7 m/s, Rj = 2 56 x lo' 



O RUN 211 U. = 7.6 m/s, Rg = 4 14 x lO' 



Ci RUN 212 U. = 8 5 m/s. Re = 4 63 x lO' 



OQD 



02 04 06 08 1.0 



U/Uo U. • SHIP. MODEL SPEED 



FIGURE 19. Velocity profile data from R/V ATHENA 

 measured at four speeds at location 1. 



corresponding data from the ship in Figures 23, 24, 

 and 25. This is the extent of the model scale 

 boundary layer data. 



The accuracy of the model scale measurements with 

 five-hole pi tot tubes is known reasonably well. 

 Model wake survey data have been repeated in past 

 experiments, with the circumferential mean longi- 

 tudinal velocity components repeating within 0.01 

 of the free stream velocity. The velocity component 

 ratios for the model data are repeatable to within 

 plus or minus one percent, except in areas where 

 steep velocity gradients occur. In the areas where 

 high velocity gradients exist, such as behind the 

 shaft struts, the five-hole pitot tube has much 

 lower accuracy. Experiments with hot wire anemom- 

 eters have shown that they are at least as accurate 

 as five-hole pitot tubes. In fact, in regions where 

 there are steep velocity gradients, hot wire anemom- 

 eters may be an order of magnitude more accurate 

 than pitot tubes . 



7. COMPARISON OF MODEL- AND FULL-SCALE DATA 



A study of the velocity component ratios presented 

 in Figures 15 through 18 shows that the degree of 

 scatter of the full-scale data is higher than that 

 of the model data. This is due to the higher 

 variations in both pressure measurement and ship 

 speed. In particular, the full-scale data for the 

 longitudinal velocity component ratio at the inner- 

 most radius (r/R - 0.456) show the largest scatter. 



