文档介绍：*pressibilty correction rule for thin wing
The effect pressibility in 3-D flows is somewhat less
dramatic than with 2-D flows, but many of the same effects
e of the same techniques for predicting
pressibility effects work in 3-D too. For example,
we can transform the 3-D Prandtl-Glauert equation into the 3-D
Laplace equation for pressible flow by changing variables
just as in 2-D.
Defining the geometry of a finite wing: y=f(x,z)
So the boundary condition is:
Transform the (x,y,z) and in the following way:
If
Derive the boundary
condition:
If
Then
The Geometry relation:
The relation of Aerodynamic coefficients:
This correction rule is Goethert Rule.
Derivation of the 3-D Prandtl-Glauert correction rule from Goethert rule:
This is the Prandtl-Glauert correction Rule
heless, changing the lift curve slope just by the Prandtl-Glauert factor does not do too badly:
A somewhat better approximation is obtained by applying the Prandtl-Glauert correction to the 2-D lift curve slope, then applying the downwash correction from lift line theory.