Airfoils Lift and Bernoullis Principle History Ancient Discoveries

Airfoils, Lift and Bernoulli’s Principle

History • Ancient Discoveries – Chinese and kites – Early flight explorers Lilienthal and Cayley in the 1800 s • Camber – A measure of the curvature of the airfoil • Airfoil – a part with a flat or curved surface, such as a wing or rudder, specifically designed to keep an aircraft in the air.

Airfoil

Airfoil Trailing Edge Leading Edge cord 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 1700 s. – 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 Tilt with respect to airflow Airflow must remain smooth – Small angle of attack; air flows smooth on the surface

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 Resources Aerospaceweb. org. (2009). Ask-Us – Parts of an airplane. Retrieved June 26, 2009, from http: //www. aerospaceweb. org/question/design/q 0101. 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. ). Foil. Sim. U beta version 1. 5 a. Retrieved June 19, 2009, from http: //www. lerc. nasa. gov/WWW/K-12/aerosim/applet/vj 402. html