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Aerodynamics

Aerodynamics. Lab 6A. Airfoil Terminology. Angle of Attack. How is Lift Produced ?. Air moving over the top of the wing has a higher velocity locally than the air on the bottom The Bernoulli Principle prescribes: Higher velocity locally = Lower pressure locally

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Aerodynamics

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  1. Aerodynamics Lab 6A Winter Quarter

  2. Airfoil Terminology Winter Quarter

  3. Angle of Attack Winter Quarter

  4. How is Lift Produced ? • Air moving over the top of the wing has a higher velocity locally than the air on the bottom • The Bernoulli Principle prescribes: • Higher velocity locally = Lower pressure locally • Lower velocity locally = Higher pressure locally • The resulting pressure difference causes a force that pushes up on the wing (aka lift) Winter Quarter

  5. Lift and Drag • Lift is defined as a force normal to the relative wind • Drag is a force parallel to the relative wind, and here is a "by-product" of producing lift Winter Quarter

  6. How Angle of Attack and Camber Affect Lift Winter Quarter

  7. What About a Symmetric (no camber) Airfoil? Winter Quarter

  8. Bottom Line: Cambered Vs Symmetric • Cambered airfoils produced lift at zero angle of attack. • Symmetric (no camber) airfoils do not produce lift at zero angle of attack Winter Quarter

  9. Sources of Drag on Airfoils • The drag that arises as a result of producing lift, called the "drag due to lift" or "induced drag" • The drag that results from friction between the air molecules and the surface of the airfoil, called "skin friction drag" • When flying near or faster than the speed of sound, the drag produced by shock waves in the flow, called "wave drag" Winter Quarter

  10. What Happens to an Airfoil when it Stalls ? • Flow over the top surface separates from the airfoil, resulting in a high pressure wake region Winter Quarter

  11. Sources of Additional Airfoil Information • How Airplanes work:http://www.howstuffworks.com/airplane4.htm • NASA’s FoilSim II airfoil simulation program:http://www.grc.nasa.gov/WWW/K-12/airplane/foil2.html • Airfoil Database (Hint: look at low Reynolds number airfoils for the upcoming lab) :http://www.aae.uiuc.edu/m-selig/ads/coord_database.html Winter Quarter

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