234 



FIGURE 15. Velocity component 

 ratios for R/V ATHENA and DTNSRDC 

 model 5365 at 0.456 radius. 



-20 20 40 63 30 100 UO 140 160 ISO 200 220 240 260 230 300 320 340 360 330 



RNGLE IN DECREES 



5. FULL-SCALE WAKE SURVEY AND BOUNDARY LAYER 

 MEASUREMENTS 



The full scale trials were run in the Atlantic 

 Ocean off the Florida Coast near the mouth of the 

 St. Johns River. The conditions for the trials 

 were excellent as is shown in Table 1, which gives 

 the trial agenda and sea conditions. The full-scale 

 measurements were divided into four trials. Trial 

 1 consisted of a wake survey in the propeller disk, 

 and ahead of the struts on the port and starboard 

 sides.* The objective of the measurements ahead of 

 the struts was to determine the differences in the 

 wake both with and without the propeller operating. 

 Trial 2 consisted of a repeat of the wake survey in 

 the propeller disk. However, for this repeat 

 trial, the two rakes ahead of the struts on the 

 starboard shaft were removed to eliminate any 

 possibility of interference in the measurements. 

 Trial 3 consisted of boundary layer profile measure- 

 ments on the port and starboard sides of the hull. 

 Again, the purpose of these measurements on both 

 sides of the ship was to determine the effects of 

 propeller induction on the development of the 

 boundary layer. Trial 4 consisted of measurements 

 of the time varying pressures in a plane ahead of 

 the operating propeller. The results of Trial 4 

 are discussed in Appendix A. 



*Note : The data from the wake surveys ahead of the struts 

 and in the propeller disk at a lower speed are not re- 

 ported in this paper, but will be reported in the future. 



The pitot tubes on the rake in the propeller 

 plane were located at non-dimensional radii (local 

 radius divided by propeller radius) of 0.456, 

 0.633, 0.781, and 0.964. The angular position of 

 the rake was adjusted by turning the entire shaft 

 using the jacking gear. The shaft could be rotated 

 through approximately 230°, and because of this an 

 overlap of 50° could be obtained in the data 

 around 180°. 



The data from the wake survey at 15 knots are 

 given, along with the corresponding model data, on 

 Figures 15 through 18. This ship speed corresponded 

 to a Froude number of 0.36 and a Reynolds number of 

 4.14 X 10^. The data are presented as velocity 

 component ratios, where the velocities are given in 

 cylindrical coordinates centered about the pro- 

 peller shaft. The longitudinal velocity component 

 (VX) is positive for flow toward the stern. The 

 tangential velocity component (VT) is taken to be 

 positive in the counterclockwise direction when 

 looking forward on the starboard shaft. The radial 

 velocity component (VR) is taken as positive in- 

 ward. The angles are defined positive in the 

 counterclockwise direction, with zero directly 

 upward. The conventions for the angles and the 

 directions of the velocity components are shown on 

 Figure 5. These conventions are those of Hadler 

 and Cheng (1965) , except that the data is presented 

 on the starboard shaft rather than on the port 

 shaft. Therefore, the angles increase in the 

 opposite direction from Hadler and Cheng, as do the 

 tangential velocity components. 



