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Aerodynamics

Aerodynamics. Dane Johannessen. Overview. Aerodynamics What are the forces? How do these forces affect flight? What factors affect these forces?. What is Aerodynamics?. The study of forces acting on an object in motion as it passes through air. Laws of Motion.

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Aerodynamics

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  1. Aerodynamics Dane Johannessen

  2. Overview • Aerodynamics • What are the forces? • How do these forces affect flight? • What factors affect these forces?

  3. What is Aerodynamics? • The study of forces acting on an object in motion as it passes through air.

  4. Laws of Motion • Objects in motion stay in motion • Force is the change in momentum with respect to time • For constant mass • For every action there is an equal and opposite reaction

  5. What are the forces? • Lift • Drag • Weight • Thrust

  6. Lift • The vertical forces pushing up on a body during flight. • General Equation: • L = Lift Force • ρ = density • v = velociy • A = area • Cl = Lift coefficient that is usually determined experimentally

  7. Lift in Air Foils • Based on pressure differences (Bernoulli’s Principle) • Top • Higher velocity and decreased pressure • Bottom • Lower velocity increased pressure • http://www.youtube.com/watch?v=zV06PgxarW0

  8. Factors Affecting Lift • Factors • Shape of object • Higher curve = greater lift • Size of the object • L = constant x A • Velocity of the object • L = constant x v² • Properties of the air • L = constant x ρ • Angle of attack • Increased angle = increased lift

  9. Demonstration • For more information on paper airplanes • Go here http://www.paperairplaneshq.com/

  10. Drag • Drag is the force that acts in the same direction as airflow • General Equation: • Fd = Drag Force • ρ = density • v = velocity • A = area • Cd = Drag Coefficient that is usually determined experimentally

  11. How Shape Affects Drag • Different shapes of the same frontal area lead to different drag coefficients:

  12. Lift to Drag Ratio • General Equation:

  13. Weight • Weight is the force on an object due to gravity • Based on mass and gravitational acceleration • General Equation: • W = Weight Force • m = mass • g = gravity

  14. Thrust • Thrust is the force that propels an object through air • General Equation: • F = thrust force • t = time • m = mass • v = velocity • ṁ = mass flow rate • ṁ = ρvA

  15. Thrust • Producers of thrust • Propellers • Fans in jet engines • Hot gases from rocket engines • Main thing to take away • Thrust must be greater than weight

  16. Thrust to Weight Ratio • General Equation: • If F/W is high • High acceleration • High Climb rate • If F/W > 1.0 • Acceleration can be vertical

  17. Summary • Aerodynamics • 4 Forces on a plane • Lift • Dependent on shape, size, velocity, air, angle • Drag • Dependent on shape • Weight • Thrust • Lift > Drag • Thrust > Weight

  18. Sources • Helpful Websites • http://www.nasa.gov/audience/forstudents/k-4/stories/what-is-aerodynamics-k4.html • http://www.grc.nasa.gov/WWW/k-12/airplane/topics.htm • http://www.paperairplaneshq.com/

  19. Questions?

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