RESISTANCE MEASUREMENTS 



Total drag has been measured using the standard DTNSRDC block-gage-type dynamo- 

 meter, mounted internally, on each model and connected to the carriage with a single stream- 

 lined strut. This dynamometer has an accuracy of approximately 1 percent at its maximum 

 load capability of 55 k. The model centerline-submergence depth was fixed at 2.74 m below 

 the water surface for all runs. The models were ballasted for a slight amount of negative 

 buoyancy with zero moment at the towing strut. Previous work has shown that the towing- 

 strut model, interference-drag coefficient is less than 0.01 • 10" 3 for the size of models 

 investigated. Since this interference drag is within the experimental accuracy of model drag 

 data reported here, no corrections have been made for it. 



TRANSITION MEASUREMENTS 



Table 3 gives the locations of the hot films in the various models. Selection of the hot 

 film locations was assisted by inspection of pressure distributions, experience from previous 

 tests, and some trial and error. When laminar separation was predicted, a hot film was 

 inserted immediately fore and aft of the predicted location. The Curie and Skan modified 

 Thwaites criterion 7 of X = -0.09 was used to predict the location of laminar separation where 

 X is a pressure gradient parameter given by 



x 6 2 dU 



X = — — (5) 



v ds 



where Q is boundary layer momentum thickness 



v is kinematic viscosity 

 U is potential flow velocity on the body 

 s is arc length along a meridian. 



The values of 6 were computed using the Granville integral method for bodies of revolution. 8 

 The computed positions of laminar separation are listed in Table 4. 



Curie, N. and S.W. Skan, "Approximate Methods for Predicting Separation Properties of Laminar Boundarv 

 Layers," Aeronautical Quarterly, Vol. 8 (1957). 



Granville, P.S., "The Calculation of the Viscous Drag of Bodies of Revolution, " David Taylor Model Basin 

 Report 849 (1953). 



