- 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
and the average skin friction coefficient is
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) |
|
