Drag Reduction by Suction 



Transition Reynolds number for different length Reynolds numbers are 

 presented in Fig. 4 as determined experimentally in the wind tunnel. The de- 

 sign value of Cq at 50 fps is 12.3 x 10"*. This value is appreciably higher than 

 an extrapolation of Fig. 4 to the design length Reynolds number of 39 x 10'' would 

 indicate is necessary. This was the first indication that the design method was 

 not sufficient. 



I X 10 





>- 



(/) 



at 



7 p 



6 ^- 



3h 



I X 10 



. 4 45 X [f 

 3 72 X ,06 





2 45 X 10* 



14 16 



-4 



Fig. 



2 4 6 8 10 12 



SUCTION COEFFICIENT- Cq x I0' 



4 - Transition Reynolds number vs suction coefficient 



Field testing of TRI-B was resumed at NTS in March 1964. In addition to 

 having the slots modified, the body incorporated more refined instrumentation. 

 10 channels of information were recorded on a galvanometer; measured were 

 the velocity, depth, pressure across the pump, time, pump rpm, velocities at 

 the tail at 3 different radial locations, and the deviation from the vertical in two 

 mutually perpendicular planes. 



The project was plagued with instrumentation difficulties throughout the 

 second series of tests. This included the failure of pressure transducers, the 

 sensitivity of differential transducers to change in temperature and absolute 

 pressure and shifting in the zero settings of the bridge outputs, possibly the re- 

 sult of a mechanical hysteresis in the transducers. 



1007 



