velocity profiles of the boundary layer are 
shown on segment X-Y of figure 1.26. In the 
area of adverse pressure gradient the bound- 
ary layer flow is impeded and tends to show a 
reduction in velocity next to the surface. If 
the boundary layer does not have sufhcient 
kinetic energy in the presence of the adverse 
pressure gradient, the lower levels of the 
boundary layer may stagnate prematurely. 
56