200 400 



600 



800 



1000 



1200 



V 



Figure 3. From Klebanoff, Schubauer and Tidstrom (21), by permission of the Journal of Aeronautical 



Sciences. 



element and its height are two independent dimensional parameters [cf. Ref. 22]. From 

 them, together with the flow variables, one can indeed construct both of the above 

 parameters, which appear to be independent. Thus, if one tries to obtain a one- 

 parameter correlation, there must be an imposed condition (or some other subtle reason) 

 which would reduce a degree of freedom. It therefore seems desirable that experiments 

 should be performed for a wide range of values of both parameters in order to clarify 

 the role of roughness. 



I wish now to make another suggestion for experiments to decide on the relative 

 significance of two effects on transition. The heating of the solid surface increases the 

 stability of the boundary layer in water by decreasing the viscosity in the immediate 



362 



