235 



0.633 Radius 



1 .2 

 1 .1 

 1 .0 



C.3 



> 



^ 0.9 



X 



> 



0.7 



0.6 



O.E, 



0.1 



0.3 



n.2 



0.1 

 > 



^ 



I— 



-0.1 

 -0.2 



0.2 

 0.1 

 

 ■0.1 

 ■0.2 



FIGURE 16. Velocity component 

 -20 20 40 50 30 100 120 140 ISO 18C 200 220 240 2S0 280 300 320 340 360 330 ratios for R/V ATHENA and DTNSRDC 



ANGLE IN DEGREES model 5365 at 0.633 radius. 



There are not sufficient data at any one radius 

 or circumferential position to adequately define 

 the limits of accuracy for the full-scale measure- 

 ments. A comparison between two different pitot 

 tubes at any one radius may be made in the region 

 between 150 and 200° where the data overlap. At 

 all radii the longitudinal velocity component 

 ratios show the greatest scatter in the full-scale 

 data. In particular at the innermost radius 

 (r/R = 0.456) , the scatter in the longitudinal 

 velocity component ratios is greatest, approxi- 

 mately plus or minus ten percent. The scatter in 

 the longitudinal velocity component ratios at other 

 radii is significantly less than that, more nearly 

 plus or minus five percent. The increased scatter 

 in the longitudinal velocity component ratios is 

 due to the computation procedure which uses the 

 average of the longitudinal velocity components 

 from both the radial and tangential velocity 

 computations . 



The full-scale wake survey provided a unique 

 opportunity to study the development of a turbulent 

 boundary layer on a ship, and also the effects of 

 propeller action on the boundary layer. The full- 

 scale boundary layer was measured at the eight 

 locations which are shown on Figures 3 and 4, at 

 four speeds. These speeds were 6.2, 9.1, 14.8, 

 and 16.5 knots; these speeds correspond to Reynolds 



numbers of 1.74 x lo"^, 2.56 x lO", 4.14 x 10», and 

 4.63 X 10^ respectively. 



The data obtained at location 1, for all four 

 speeds, are plotted on Figure 19. Except for the 

 data at 6.2 knots, which show a great deal of 

 scatter, the data are quite consistent with the 

 fullness of the boundary layer increasing as the 

 Reynolds number increases. The data obtained at 

 14.8 knots (R = 4.14 x 10^) for location 1, 2, and 

 3 are plotted in Figures 20, 21, and 22 along with 

 the corresponding model data at the same Froude 

 number. The data from Locations 1, 2, and 3 are 

 plotted again in Figures 23, 24, and 25 along with 

 the data for the corresponding locations on the 

 port side with the propeller operating. 



6. MODEL-SCALE WAKE SURVEY AND BOUNDARY LAYER 

 MEASUREMENTS 



For the model-scale wake survey. Model 5365 was 

 ballasted while at rest to the drafts corresponding 

 to those of the ship during the full-scale wake 

 survey. The model was then towed at 5.22 knots 

 (2.685 m/s) , the Froude-scaled speed which corre- 

 sponds to 15 knots full-scale. The velocity com- 

 ponent ratios were measured with a rake of five-hole 

 pitot tubes at radii corresponding exactly to the 



