text: forward stagnation point 
  the local velocity 
  is zero and the maximum positive pressure re- 
  sults. As the flow proceeds from the forward 
  stagnation point 
  increases as 
  shown by the change in streamlines. The 
  local velocities reach a maximum at the upper 
  and lower extremities and a peak suction pres- 
  sure is produced at these points on the cylinder. 
  (NOTE: Positive pressures are pressures above 
  atmospheric and negative or .ruction pressures 
  are less than atmospheric.) As 
  flow 
  continues aft from the peak suction pressure, 
  the diverging streamlines indicate decreasing 
  local velocities and increasing local pressures. 
  If friction and compressibility effects are not 
  considered, the velocity would decrease to zero 
  at the aft stagnation point and the full stagna- 
  tion pressure would be recovered. The pressure 
  distribution 
  for the cylinder in perfect fluid 
  flow would be symmetrical and no net force 
  (lift or dragj wvuid rcsuit. Of course, thr 
  relationship between static pressure and ~eloc- 
  ity along the surface is defined by Bernoulli’s 
  equation. 
  
  the velocity 
  
  GENERATION OF LIFT. An important 
  the production 
  phenomenon associated with 
  im- 
  of lift by an airfoil 
  parted to the airstream. The best practical 
  illustration of this phenomenon is shown in 
  figure 1.8 by the streamlines and pressure dis- 
  tributions existing on cylinders in an airstream. 
  The cylinder without circulation has a sym- 
  metrical streamline pattern and a pressure dis- 
  tribution which creates n-0 n_et lift. 
  If the 
  is given a clockwise rotation and 
  cylinder 
  induces a rotational or circulatory flow, a dis- 
  tinct change takes place in the streamline pat- 
  tern and p’ess.~re &str~‘“u~~oii, The vriocitirs 
  due to the vortex of circulatory 
  flow cause 
  increased 104 velocity on the upper surface 
  of the cylinder and decreased local velocity on 
  the lower surface of the cylinder. Also, the 
  circulatory flow produces an upwash immedi- 
  ately ahead and downwash immediately be- 
  hind the cylinder and both fore and aft stagna- 
  tion points are lowered. 