Flat Plate

(Book 20.1)

We want to derive the Blasius steady boundary layer on a semi-infinite flat plate:

Continuity:

x-Momentum:

Note that since the velocity is constant, U, in the matching region, the pressure must be constant.

Try a similarity solution. If is a typical boundary layer thickness:

Typical boundary layer thickness:

Shape of the velocity profile: with

Numerical solution produces f''(0)=0.33206, which fixes the wall shear.

Exercise:

Find the shear force on a plate of length 0.5 m moving flush through air at a speed of 0.5 m/sec

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