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11 Oct 6 - Drag Polar, Config Aero and 3D effects

# 11 Oct 6 - Drag Polar, Config Aero and 3D effects - AOE...

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AOE 2104--Aerospace and Ocean Engineering Fall 2009 Virginia Tech 6 October 2009 Lecture 6 AOE 2104 Introduction to Aerospace Engineering Lecture 6 Drag Polar Basic Aerodynamic Configurations

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Virginia Tech Are there any questions on how to complete the problems from the first assignment? General questions on the new HW Quiz 3 is coming!!! Mark your calendars for October 20 th . AOE 2104--Aerospace and Ocean Engineering Fall 2009 6 October 2009 Lecture 6
Virginia Tech What is the difference between a wing and an airfoil? What’s the camber line? Chord line? What is stall? Describe the process leading to stall? Describe the main characteristics of a lift curve. What are the different types of drag? How does drag vary with angle of attack? What’s the name of the drag versus lift curve? What’s the aerodynamic center? The center of pressure? What is the coefficient of pressure? What is aspect ratio? Give 2 reasons why airfoil data can’t be used to infer wing performance. Some things to think about…. AOE 2104--Aerospace and Ocean Engineering Fall 2009 6 October 2009 Lecture 6

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Virginia Tech AR e C C C L d D π 2 + = Aerodynamic shapes – Drag Summary We saw that the airfoil drag consisted in the summation of: Skin Friction Drag Pressure Drag Wave drag (due to shockwaves, negligible for incompressible flows) Similarly, the wing drag is given by Di p d f d D C C C C + + = , , Di d D C C C + =  “drag polar” Profile Drag Induced Drag AOE 2104--Aerospace and Ocean Engineering Fall 2009 6 October 2009 Lecture 6
Virginia Tech Aerodynamic shapes – Drag Polar AR e C C C L d D π 2 + = AOE 2104--Aerospace and Ocean Engineering Fall 2009 6 October 2009 Lecture 6

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Virginia Tech Aerodynamic shapes – Consequences on the lift distribution One way to obtain such distribution is to have an elliptical wing (where the chord varies elliptically spanwise). This has been used on some aircrafts and sailplanes to minimize drag. It is also possible to obtain elliptical loading by careful combinations of sweep, taper, twist, and spanwise variations of the airfoil section . The span efficiency factor e , or Oswald Efficiency factor , is a measure of how well the wing planform is designed (in terms of drag production) and has values between 0 and 1 . The minimum induced drag occurs when Oswald efficiency e = 1 . The wing is then said to have an elliptical spanwise lift distribution or elliptical loading. AOE 2104--Aerospace and Ocean Engineering Fall 2009 6 October 2009 Lecture 6
Aerodynamic shapes – Elliptical Loading through Wing Shape http://www.richard-seaman.com/Aircraft/AirShows/Chino2004/Sampler/ http://history.sandiego.edu/gen/st/~jgaffney/aviation/ww2.html One major disadvantage of elliptical wings: very difficult to manufacture . Hence, few airplanes with elliptical wings were built.

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11 Oct 6 - Drag Polar, Config Aero and 3D effects - AOE...

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