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ME 388 – Applied Instrumentation Laboratory Wind Tunnel Lab

ME 388 – Applied Instrumentation Laboratory Wind Tunnel Lab. References. Munson, Young and Okiishi, Fundamentals of Fluid Mechanics Zucker, Fundamentals of Gas Dynamics Zucrow and Hoffman, Gas Dynamics Any fluids text. Experimental Objectives. Measure lift and drag forces

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ME 388 – Applied Instrumentation Laboratory Wind Tunnel Lab

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  1. ME 388 – Applied Instrumentation Laboratory Wind Tunnel Lab

  2. References • Munson, Young and Okiishi, Fundamentals of Fluid Mechanics • Zucker, Fundamentals of Gas Dynamics • Zucrow and Hoffman, Gas Dynamics • Any fluids text

  3. Experimental Objectives • Measure lift and drag forces • NACA 0012 airfoil (National Advisory Committee on Aeronautics) • At various angles to air stream • Determine coefficients of lift and drag and compare to published values • Determine coefficients of lift and drag at the stall angle

  4. Wind Tunnel Testing • Allows engineers to predict the amount of lift and drag that airfoils can develop in various flight conditions. • A 747 aircraft can weigh over 200,000 lbs.

  5. 2D Components of Lift and Drag • Resultant force due to airflow across an asymmetric body is not in the direction of the airflow

  6. Lift • Generated by pressure difference over the airfoil when the air moving over the body takes a different path to reach the same point

  7. Drag • Result of fluid friction • Opposes body motion

  8. Lift and Drag Dependence • Size • Shape • Fluid flow • Principle of Similitude allows us to “non-dimensionalize” these parameters

  9. Wind Tunnel and Instrumentation

  10. NACA 0012 Air Foil

  11. Scaled-down Physical Modeling • Consider size for a given shape

  12. Lift and Drag Plots

  13. Lab Measurements • Drag and Lift forces are measured with a dynamometer • Chord and width are measured with a ruler • Air velocity is measured with a Pitot tube • Angle of attack is measured with a protractor

  14. Fluid Conditions • For similitude, fluid conditions must also be similar • Fluid flow is non-dimensionalized via the Reynolds number

  15. Pitot Tube and Bernoulli Eqn. • Frictionless flow with only mechanical energy • No heat transfer • No change in internal energy

  16. Calibrate Dynamometer

  17. Calibration Procedure • Remove air foil from dynamometer post • Attach string and weights from dynamometer post and calibrate (use weights to at least 1000 g) • Remove weights and turn-on wind tunnel and adjust for air velocity for Re = 160,000 • Record voltages from dynamometer • Turn-off air and re-install air foil • Record voltage (weight) of airfoil • Run experiment

  18. Dynamometer Calibration Curves

  19. Experimental Procedure • Let dynamometer heat-up 15 minutes before taking data • Adjust airfoil to 0° attack angle and take dynamometer reading • Take readings every 3° • When lift force decreases (voltage drops), decrease attack angle in 1° increments to determine stall angle

  20. Lab Requirements Summary • Develop dynamometer calibration curves • Plot lift and drag coefficients as a function of attack angle • Compare data to published NACA 0012 data at Re = 160,000, and for a flat plate • Determine angle of maximum lift, a.k.a. the stall angle • Calculate uncertainty of the lift coefficient at the stall angle

  21. In 1915, the U.S. Congress created the National Advisory Committee on Aeronautics (NACA -- a precursor of NASA). During the 1920s and 1930s, NACA conducted extensive wind tunnel tests on hundreds of airfoil shapes (wing cross-sectional shapes). The data collected allows engineers to predictably calculate the amount of lift and drag that airfoils can develop in various flight conditions. Reference?

  22. NASA Photo

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