text: delay the transition to some point farther aft 
  on the chord. The subsequent reduction in 
  friction drag at the low angles of attack ac- 
  counts for the “drag bucket” shown on the 
  graphs of cd and cI for 
  these sections. Of 
  course, the advantages of the laminar flow 
  airfoil are apparent only for the smooth airfoil 
  since surface roughness or waviness may pre- 
  clude extensive development of a laminar 
  boundary layer. 
  
  AIRFLOW SEPARATION. The character 
  of 
  the boundary layer on an aerodynamic 
  surface is greatly influenced by the pressure 
  In order to study this effect, the 
  gradient. 
  pressure distribution of a cylinder in a perfect 
  fluid is repeated in figure 1.26. The airflows 
  depict a local velocity of !zero at the forward 
  stagnation point and a maximum local velocity 
  at the extreme surface. The airflow moves 
  from the high positive pressure to the minimum 
  favorable pressure gradient 
  pressure point-a 
  (high 
  As the air moves from the 
  to low). 
  extreme surface aft, the local velocity decreases 
  to zero at the aft stagnation point. The static 
  pressure increases from the minimum (or max- 
  imum suction) to the high positive pressure 
  at the aft stagnation point-an 
  adverse pres- 
  sure gradient (low 