37 



transition point from laminar to turbulent flow. It is customary to use the 

 value of 6 of the laminar boundary layer at the transition point as the ini- 

 tial value of 6 for the turbulent boundary layer. Owing to the lack of reli- 

 able data on transition, the initial value of H may be taken as that for a 

 flat plate at the same Reynolds number R fl . 



The evaluation of 6 and H is required in many technical hydro- 

 dynamic and aerodynamic applications involving calculations of drag and of 

 velocity profiles of boundary layers. According to the following formula of 

 Squire and Young 11 for the profile drag of airfoils, $ and H must be deter- 

 mined at the trailing edge 



i> - p-i£ » 4 (jf ) [85: 



where the subscript t refers to conditions at the trailing edge. If a power- 

 law distribution is assumed, the values of and H at any station along the 

 boundary layer specify the shape and thickness of the velocity profile, as 

 shown by Equation [l6], 



A knowledge of the characteristics of the velocity profiles of boundary layers 

 is required for the design of control surfaces and propellers on forms moving 

 in fluids and of the various conduit sections of water and wind tunnels. 

 Large values of H indicate the danger of flow separation for cases involving 

 adverse pressure gradients. 



ACKNOWLEDGMENTS 



The author wishes to express his thanks to Mr. M.P. Tulin, Dr. A. 

 Borden and Mr. P. Eisenberg for their critical review of this report. The 

 general form for the auxiliary equation, Equation [84], was suggested by 

 Mr. Tulin. 



