Airfoils Lift Bernoulli's Principle Fixed2
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Transcript of Airfoils Lift Bernoulli's Principle Fixed2
Airfoils, Lift andBernoulli’s Principal
History
• Ancient Discoveries– Chinese and kites– Early flight explorers Lilienthal and Cayley in
the 1800s
• Camber– Top of the airfoil curved like a hump
Airfoil
Airfoil
Trailing Edge Leading Edge
Angle of Attack
Bernoulli’s Principle
The pressure of a fluid decreases as the speed of the fluid increases– The principle was first discovered in the
1700s.– When a fluid moves quickly, its pressure
decreases.– Since air is considered a fluid, this
principle can be applied to the design of a wing.
Lift
Bernoulli’s Principle– When a fluid
moves fast, its pressure decreases.
– Since air is considered a fluid, this principle can be applied to the design of a wing.
Bernoulli’s Principle
• Both streams must meet at the end of the wing at the same time.
• Stream A has farther to go; therefore, it must travel faster.
Bernoulli’s Principle
• Bernoulli proved that as fluids move faster, their pressure decreases.
• This principle explains why a plane rises.
Factors that Affect Lift
The Object: Shape and Size
The Motion: Velocity and Angle of Attack
The Air: Mass, Viscosity, Compressibility
Factors that Affect Lift
The Object – Wing geometry– Airfoil shape– Wing size– Aspect ratio: Mathematical relationship
between the wing span (overall length) to the wing area
Factors that Affect Lift
Motion – Move the object– Velocity (speed)– Angle of attack (how the object is tipped
toward the wind)
Factors that Affect Lift
Air – Mass– Viscosity
• Stickiness
– Compressibility• Springiness
– Density Altitude• Density of air molecules at a given altitude
Airfoil Shapes and Lift
Wing or Airfoil?– Airfoil is a shape
designed to generate as much lift as possible while incurring as little drag as possible.
– The wing is attached to a plane and must take into consideration drag and the lift created.
Angles and Airfoils
Angle of Incidence– The tilt of the wing with respect to its
attachment to the body of the airplane (fuselage)
Angles and Airfoils
Angle of Attack– The tilt of the airfoil with respect to the airflow
Angles and Airfoils
Airflow must remain smooth– Small angle of
attack; air flows smooth on the surface
Tilt with respect to airflow
Angles and Airfoils
Angle of attack becomes too steep– Airflow is disrupted
and the airplane loses lift or stalls
– Critical Angle of Attack is the point where it stalls
Angles and Airfoils
Causes of stall– Flying at too steep an angle– Real-life flying situations
• Sudden gust of wind decreases the plane’s forward speed, decreasing the airflow over the wing
• Flying too slow (indicated airspeed)
– Wing icing• Changes the shape of the airfoil
Amount of Lift
Amount of lift produced by an airfoil depends on may factors– Angle of attack– Lift devices used (flaps, etc.)– Density of the air– Area of the wing– Shape of the wing– Speed at which the wing is traveling
Now follow along as we prove Bernoulli’s Principle is True!
Image ResourcesAerospaceweb.org. (2009). Ask-Us – Parts of an airplane. Retrieved
June 26, 2009, from http://www.aerospaceweb.org/question/design/q0101.shtml
Microsoft, Inc. (2008). Clip art. Retrieved June 26, 2009, from http://office.microsoft.com/en-us/clipart/default.aspx
National Aeronautics and Space Administration (NASA). (n.d.). Virtual skies: Aeronautics tutorial. Retrieved June 24, 2009, from http://virtualskies.arc.nasa.gov/aeronautics/tutorial/intro.html
National Aeronautics and Space Administration (NASA). (n.d.). FoilSimU beta version 1.5a. Retrieved June 19, 2009, from http://www.lerc.nasa.gov/WWW/K-12/aerosim/applet/vj402.html