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ME403 Chapter 2 2D Airfoil Aerodynamics

ME403 Chapter 2 2D Airfoil Aerodynamics. Lift is mainly provided by the wing with an airfoil cross-section shape. Airfoil Geometry. An airfoil is the 2D cross-section shape of the wing, which creates significant lift but minimal drag because of this aerodynamic shape. Historical Airfoils.

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ME403 Chapter 2 2D Airfoil Aerodynamics

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  1. ME403 Chapter 2 2D Airfoil Aerodynamics Lift is mainly provided by the wing with an airfoil cross-section shape

  2. Airfoil Geometry An airfoil is the 2D cross-section shape of the wing, which creates significant lift but minimal drag because of this aerodynamic shape

  3. Historical Airfoils

  4. Historical Airfoils

  5. Typical Streamlines Angle of Attack

  6. Pressure Distribution

  7. Pressure Coefficient Distribution In the uniform free-stream: At the stagnation point (at which velocity V=0): Positive Cp means the pressure is higher than the free-stream (atmospheric) pressure, and negative Cp means suction relative to free-stream pressure. The maximum, which occurs at the stagnation point, is always 1.

  8. Viscous Boundary Layer Velocity profile creates skin friction (shear) drag on surface

  9. Flat Plate Skin Friction Drag Coefficient Curve fit formula for turbulent boundary layer (Re > 500,000):

  10. Evolution of Airfoil Design Delaying transition point from Laminar to Turbulent boundary layer reduces skin friction drag

  11. Boundary Layer Flow Separation When flow separation occurs, there is also pressure drag.

  12. Pressure (Form) Drag due to Flow Separation 100% Pressure Drag Total Profile Drag = Skin Friction Drag + Form Drag

  13. Resultant Aerodynamic Force

  14. Lift & Drag Coefficients

  15. Center of Pressure The resultant aerodynamic force acts at the Center of Pressure (c.p.), about which the moment is zero.

  16. Open-Circuit Wind Tunnel

  17. Wind Tunnel Tests Force transducer behind model senses lift, drag and pitching moment directly. Motor-controlled mechanism adjusts the model’s angle of attack.

  18. Closed-Circuit Wind Tunnel

  19. Wing Section Models Model for measuring lift, drag and pitching moment Model for measuring surface pressure distribution

  20. NACA 0006 Data at Re = 3,180,000 There is a maximum Lift-to-Drag ratio (L/D). Location of Center of Pressure (c.p.) varies with a

  21. NACA 2312 Data at Re = 3,120,000 Lift decreases and drag increases sharply beyond the stall (max. Cl) point, due to boundary layer separation.

  22. NACA Airfoils and Test Data 4-Digit Series 5-Digit Series 6 Series http://naca.larc.nasa.gov/reports/1945/naca-report-824/

  23. Stalled Airfoil

  24. Reynolds Number Effect

  25. Aerodynamic Center Since the c.p. varies with a, it is more desirable to use a fixed Aerodynamic Center (a.c.) as the point of action of the lift and drag. The pitching moment about this point can be calculated, and is found insensitive to a. For most airfoils, the a.c. locates at around quarter chord (x=c/4). Pitching Moment Coefficient:

  26. Typical Non-Cambered AirfoilLift Curve & Drag PolarNACA 0006

  27. Typical Cambered AirfoilNACA 2412 Lift Curve & Drag Polar

  28. Typical Airfoil Aerodynamic Characteristicsat Re = 6 million

  29. Computation Fluid Dynamics Simulation

  30. CFD Simulation: Near stall

  31. CFD Simulation: Fully Stalled

  32. Airfoil Generator at http://www.ae.su.oz.au/aero/info/index.html

  33. Airfoil Analysis Code at http://www.ae.su.oz.au/aero/info/index.html

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