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Unformatted text preview: Lecture F3 Mud: Aerodynamic Forces and Moments (36 respondents) 1. What exactly is the angle of attack? (1 student) It’s the angle between the freestream direction and the body’s reference line. The freestream direction is defined to be parallel to vector V ∞ . The body reference line is arbitrary, but on an airfoil it’s traditionally chosen to be the chord line, which connects the leading edge and trailing edge points. 2. How do you generate a pressure distribution? (1 student) There are a number of analytical and numerical methods for computing the pressures on a given airfoil shape. We will cover a few of these in Unified. 3. In the integral for the lift: L ′ = ( p l − p u ) dx don’t you need to consider the shape of the airfoil? (1 student) If we neglect τ , the exact formula for the normal force is N ′ = ( p l − p u ) dx , which doesn’t depend on the shape y ( x ) at all. The key substitution is ds cos θ = dx (see notes and Anderson for more details). A physical explanation is that pressure acts only on the “projected” area dx , and the vertical height of the airfoil doesn’t matter. , and the vertical height of the airfoil doesn’t matter....
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This note was uploaded on 01/28/2012 for the course AERO 16.01 taught by Professor Markdrela during the Fall '05 term at MIT.
- Fall '05