26 



2.4 



. 2.0 



Re t x I0" 6 

 1.6 



1.2 



8 



2- DIMENSIONAL 

 ROUGHNESS 



(CYLINDRICAL RODS) 



3-DIMENSI0NAL ROUGHNESS 

 (SPHERES) 



A 3k _INCH AT 2 FEET 



& -L-INCH AT l FOOT 

 32 



— -INCH AT 2 FEET 

 16 



x -L-INCH AT 2 FEET 

 8 



+ -g--INCH AT I FOOT 



SPACING EFFECT 



,2 DIAMETERS 

 -8 DIAMETERS 



20 



Figure 2. From Klebanoff, Schubauer and Tidstrom (21), by permission of the Journal of Aeronautical 



Sciences. 



361 



