• With the profile known, wall shear can be evaluated as

Now,
or
or
	from Table 28.1

(Wall Shear Stress)

(29.1a)

and the local skin friction coefficient is

• Substituting from (29.1a) we get

  (Skin Friction Coefficient)

  (29.1b)

  
  
• In 1951, Liepmann and Dhawan , measured the shearing stress on a flat plate directly. Their results showed a striking confirmation of Eq. (29.1).
• Total frictional force per unit width for the plate of length L is

or                 

or          

(29.2)

and the average skin friction coefficient is

(29.3)

where, .

For a flat plate of length L in the streamwise direction and width w perpendicular to the flow, the Drag D would be

(29.4)