文档介绍：CHAPTER 11
PRESSIBLE FLOW OVER AIRFOILS: LINEAR THEORY
PRANDTL-PRESSIBILITY
CORRECTION
The methods that approximately take into account of
the effects pressibility by correct the pressible flow results is pressible corrections.
We will derive the most widely known correction of Prandtl-pressibility correction in this section.
Since the Prandtl-Glauert method is based on the linearized
perturbation velocity potential equation:
So it has restrictions: thin airfoil at small angle of attack;
purely subsonic;
give inappropriate results at
Boundary Condition :
In (x,y) space:
In transformed space:
So
This Equation implies that the shape of the airfoil in the transformed
space is the same as the physical space. Hence, the above tranforma-
tion relates pressible flow over an airfoil in (x,y) space to the
in space over the same airfoil.
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PRESSIBILITY
CORRECTIONS
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CRITICAL MACH NUMBER
In this section we deal with several aspects of transonic flow
from a qualitative point of view.
What is the definition of
Critical Mach Number?
The critical Mach number
is that free stream Mach
number at which sonic flow
is first achieved on the
airfoil surface.