Transcript Aerodynamics - thecollaboratoryonline.org

Dane Johannessen
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Aerodynamics
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What are the forces?
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How do these forces affect flight?
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What factors affect these forces?
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The study of forces acting on an object in
motion as it passes through air.
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Objects in motion stay in motion
Force is the change in momentum with respect
to time
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For constant mass
For every action there is an equal and opposite
reaction
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Lift
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Drag
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Weight
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Thrust
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The vertical forces pushing up on a body
during flight.
General Equation:
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L = Lift Force
ρ = density
v = velociy
A = area
Cl = Lift coefficient that is usually determined
experimentally
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Based on pressure differences (Bernoulli’s
Principle)
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Top
 Higher velocity and decreased pressure
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Bottom
 Lower velocity increased pressure
http://www.youtube.com/watch?v=zV06PgxarW0
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Factors
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Shape of object
 Higher curve = greater lift
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Size of the object
 L = constant x A
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Velocity of the object
 L = constant x v²
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Properties of the air
 L = constant x ρ
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Angle of attack
 Increased angle = increased lift
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For more information on paper airplanes
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Go here http://www.paperairplaneshq.com/
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Drag is the force that acts in the same direction
as airflow
General Equation:
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Fd = Drag Force
ρ = density
v = velocity
A = area
Cd = Drag Coefficient that is usually determined
experimentally
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Different shapes of the same frontal area lead
to different drag coefficients:
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General Equation:
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Weight is the force on an object due to gravity
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Based on mass and gravitational acceleration
General Equation:
 W = Weight Force
 m = mass
 g = gravity
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Thrust is the force that propels an object
through air
General Equation:
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F = thrust force
t = time
m = mass
v = velocity
ṁ = mass flow rate
 ṁ = ρvA
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Producers of thrust
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Propellers
Fans in jet engines
Hot gases from rocket engines
Main thing to take away
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Thrust must be greater than weight
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General Equation:
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If F/W is high
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High acceleration
High Climb rate
If F/W > 1.0
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Acceleration can be vertical
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Aerodynamics
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4 Forces on a plane
 Lift
 Dependent on shape, size, velocity, air, angle
 Drag
 Dependent on shape
 Weight
 Thrust
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Lift > Drag
Thrust > Weight
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Helpful Websites
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http://www.nasa.gov/audience/forstudents/k4/stories/what-is-aerodynamics-k4.html
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http://www.grc.nasa.gov/WWW/k12/airplane/topics.htm
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http://www.paperairplaneshq.com/