23 











,TMB Tanker Model 4083 

 Wire Diameter d - 0.032" 











o 





\o 





















> 



^s 



\ 

























^ ' 



^ 





— -d = 0.036" 1 Fage and Preston 

 v d = 0.0235" J Model H 











N 



























\ 

 \ 

























° \ 



\ 

























\ 



-aLj 











100 



200 



300 



400 



500 



600 



Reynolds Number of Trip Wire R - Ud/v 



Figure 17 - Comparison of the Position of the Onset of Transition 

 on TMB Tanker Model and on a Body of Revolution 



The trip wire Reynolds number is based upon the free-stream speed D for both models. 



conditions cannot be accomplished with the hot-wire apparatus at the present 

 state of development. It is, nevertheless, important to be able to delineate 

 the regions of laminar, transitional, and turbulent flow and for this reason 

 the qualitative application of the hot wire is extremely useful. In addition, 

 the results of the survey may be used to obtain a numerical estimate of the 

 error or decrement in the frictional resistance of the ship model, as shown 

 in the next section of this report. 



QUANTITATIVE ANALYSIS OP HOT-WIRE DATA 



An estimate of the decrement or "error" in the frictional resistance 

 of the ship model can be obtained from the qualitative determination of the 

 boundary-layer flow. The formula used to estimate the frictional resistance 

 of any model expresses the turbulent frictional drag of a flat plate of the 

 same length and wetted surface and towed at the same Reynolds number as the 

 model. Hence the region on the model which is covered by laminar flow does 

 not contribute as much resistance as dt would were it covered by a turbulent 

 layer. The decrement in the frictional resistance may be taken as the differ- 

 ence between the turbulent and the laminar drag of that region of the hull 

 which has been found to be covered by a laminar boundary layer. 



