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Unformatted text preview: EAS 4101 Aerodynamics Spring 2009 04/08/09, Exam #2 Name: ____________________________ 1 I. True/False (10 points total 1 point each) Clearly circle T for true statements and F for false statements. 1. The lift force is always perpendicular to the chord line. T F 2. Kelvins Theorem relates lift and circulation. T F 3. Wing tip vortices are driven by the pressure difference between the upper and lower surfaces of a wing. T F 4. The effective angle of attack on a wing is always less than the geometric angle of attack. T F 5. The lift slope of a finite wing is always less than the lift slope of the corresponding airfoil. T F 6. The induced drag is not a function of wing geometry T F 7. The zero lift angle of attack for a symmetric airfoil is always zero. T F 8. Induced drag coefficient is proportional to g G . T F 9. The vorticity field is always solenoidal (i.e. divergence-free). T F 10. For a general lift distribution on a finite wing, the downwash is constant over the entire span. T F II. Fill in the Blank (17 points total 1 point each) 11. The ____ center of pressure _____ is the distance from the leading edge of an airfoil to the point where there is zero aerodynamic moment. The ____ aerodynamic center _____ is the distance from the leading edge of an airfoil to a point about which the aerodynamic moment does not change with angle of attack. For a ___ symmetric ____ airfoil of chord c , these points lie on top of each other and are at a distance ____ c/4 ___ from the leading edge. 12. The Kutta condition is naturally enforced at the trailing edge due to ___ friction _____ forces. 13. The point on an airfoil about which the aerodynamic moment is zero is called the __ center of pressure _____. 14. Stokes Theorem is used show that ___ vorticity ___ is ___ circulation ___ per unit area. 15. Kelvins theorem states _______ = 0 _______ (mathematical definition). 16. In classic thin airfoil theory, an airfoil may be approximated by replacing it with a single vortex sheet distributed over the _________ mean camber line ________. This line is equal to the ___ chord line ____ for a symmetric airfoil which has a lift slope of _____ 2 _____. 17. Downwash modifies the incoming freestream velocity by producing a ______ local relative wind _____, which effectively decreases the __ angle of attack ____ and increases the ___ drag _____ on the wing. 18. Physically, the lift distribution on a finite wing is ___ symmetric ___ about the x-axis and is zero at the ___ wingtips ___. EAS Name: ____________________ III. Short Answer (18 points t 19. Consider a vortex filament Starting with the Biot-Sava the loop in terms of and R about the vortex line in the Solution: gG = , where e is a unit vector perpend = u gG 20. Given two possible shape bottom surface velocities state the Kutta condition Case 1: Finite Angl V 1 = V 2 = For both cases, 4101 Aerodynamics Spring 2009...
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This note was uploaded on 09/05/2011 for the course EAS 4101 taught by Professor Sheplak during the Spring '08 term at University of Florida.
- Spring '08