Question: Air at 26°C and 1 atm pressure flows normally to a 5 cm diameter circular cylinder at a velocity of 9 m/s. It can be shown from potential flow theory that in the vicinity of the forward stagnation point for flow normal to a cylinder the velocity along the surface, a; (which is the velocity just outside of any boundary layer), is given by
u∞ = 4Vx
D
where V is the oncoming normal velocity, x is the distance along the surface measured from the stagnation point, and D is the diameter of cylinder. Calculate the displacement thickness of the boundary layer at the stagnation point, and discuss the significance of the result.