242 



r/R = 456 



120 160 200 240 



ANGLE IN DEGREES 



Velocity Component Ratios Predicted and Measured Full-Scale 

 Trial 2, Vs = 7 87nn/s 



120 160 200 240 

 ANGLE IN DEGREES 



Velocity Component Ratios Predicted ond Measured Full-Scale 

 Trial 2, Ve = 7 87m/s 



FIGURE 29. Predicted and measured values of velocity 

 component ratios for R/V ATHENA at 0.456 radius. 



FIGURE 31. Predicted and measured values of velocity 

 component ratios for R/V ATHENA at 0.781 radius. 



U /U = ri„3/18a,x'^ 



ax 



' -""1' 



and 



11^3/23^, = lOD/tigPUo 



where V^^^ is the velocity defect, Uq the free- 

 stream velocity, n is the nondimensional wake half 

 width, X is the nondimensional distance from the 

 strut, D is the strut drag, and p the fluid density. 

 These formulas predict the longitudinal velocity 

 defect in terms of the strut drag, wake thickness, 

 and distance behind the strut. 



The shaft struts on R/V ATHENA are Navy EPH 

 sections with a chord- to- thickness ratio of 5. 



Assuming that the drag on the EPH section would not 

 be too different from the drag on an elliptic 

 section of the same thickness-chord ratio, many data 

 for a number of elliptic sections v;ere collected. 

 These data are plotted on Figure 33 as a function 

 of Reynolds number. 



The nondimensional wake half-width was predicted 

 using Equation (4) from Silverstein et al. (1938) : 



0.6£ 



C (X + 0.15) 



In this equation n is again the nondimensional half 

 width of the wake, X is the nondimensional distance 

 from the strut, and C is the drag coefficient per 

 unit length of the strut. 



Using the strut Reynolds numbers based on chord 

 length, of 1.46 x 10^ for the ship, the correspond- 



r/R = 633 



r/R =0 963 



40 



80 



280 320 



360 



120 160 200 240 

 ANGLE IN DEGREES 



Velocity Component Ratios Predicted and Measured Full-Scale 

 Trial 2, Vs = 7e7m/s 



II 



10, 

 09 

 



07 



0.6 



5 



4 



3 



02 



I 







_0 I 



.02' 



"0 40 80 120 160 200 240 280 320 360 



ANGLE IN DEGREES 



Velocity Component Ratios Predicted and Measured Full-Scale 

 Trial 2, Vs = 7 87m/s 



FIGURE 30. Predicted and measured values of velocity 

 component ratios for R/V ATHENA at 0.6 33 radius. 



FIGURE 32. Predicted and measured values of velocity 

 component ratios for R/V ATHENA at 0.96 3 radius. 



