Blasius Flow Over A Flat Plate
- The classical problem considered by H. Blasius was
- Two-dimensional, steady, incompressible flow over a flat plate at zero angle of incidence with respect to the uniform stream of velocity
 .
- The fluid extends to infinity in all directions from the plate.
The physical problem is already illustrated in Fig. 28.1
- Blasius wanted to determine
(a) the velocity field solely within the boundary layer,
(b) the boundary layer thickness  ,
(c) the shear stress distribution on the plate, and
(d) the drag force on the plate.
- The Prandtl boundary layer equations in the case under consideration are
The boundary conditions are
 | (28.16) |
- Note that the substitution of the term
 in the original boundary layer momentum equation in terms of the free stream velocity produces  which is equal to zero.
- Hence the governing Eq. (28.15) does not contain any pressure-gradient term.
- However, the characteristic parameters of this problem are
 that is, 
- This relation has five variables .
- It involves two dimensions, length and time.
- Thus it can be reduced to a dimensionless relation in terms of (5-2) =3 quantities ( Buckingham Pi Theorem)
- Thus a similarity variables can be used to find the solution
- Such flow fields are called self-similar flow field .
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