29 



the decrements calculated for the nonstimulated and the stimulated condition, 

 viz . , 



4C* 



= L 



?c 



[13] 



4C* 



where 



is the ratio of the increase in frictional resistance to the equiv- 

 alent flat-plate resistance as computed from the boundary -layer 

 survey data , 



is the computed decrement of resistance caused by the laminar 

 flow over tne model without turbulence stimulation, and 



is the computed decrement of frictional resistance caused by the 

 laminar flow which persists when the model is towed with a stimu- 

 lator. 



Curves of AQ* f /C f have been drawn on Figure 21 where it may again be observed 

 that the turbulence rod appears to be relatively better than the other devices 

 which were tested. It should be noted, however, that the values of AC* at 

 low Reynolds numbers (R < 6 x TO 6 ) are probably somewhat high because of the 

 extensive region of transitional flow obtained with turbulnnce stimulation, as 

 shown in Figure 19- No allowance has been made for the decrement arising from 

 transitional flow in any of the calculations. 



It now remains to show that the predicted increases in resistance ob- 

 tained from the boundary-layer surveys can be correlated with the increases 

 measured by the towing dynamometer under the same conditions of stimulation. 



Hote: Relation of scales of 



/I 



valid only for fresh water temperature of 7^° 3? 

 I I I 



Rod 48 Diameters Forward of Stem 

 1.032" D) 



6.0 8.0 10.0 



Model Reynolds Number R = Ul_/v 



/L 



Figure 21 - Curves of Computed Increase in Frictional Resistance of Tanker 

 Model Determined from Boundary-Layer Surveys with Various Stimulators 



