Berry Jackie

8/12/2019 Berry Jackie

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Low Speed Aerodynamics

By Jackie Berry

http://www.coolhdwallpapers.com/small_airplane_flying-wallpapers


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Topics to Cover

History of Flight How Airplanes Fly Lift

Thrust

Drag

Characteristics ofLow Speed Aerodynamics


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The History of Flight Prior to the 17th century, very little was discovered

concerning the nature of flight.

1505 Da Vinci discovered that the center of gravity is notthe same as the center of pressure and sketched a flyingmachine that resembled a bird (ornithopter).

Newton developed the first theory for air resistance. Hethought that drag was due to the shape of the flying object,

the density of the fluid, and the velocity of the object(squared). Correct for low flow speeds.

Newton developed an equation for the drag force: F =SV2sin2(). But only works for hypersonic flow speeds.


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The History of Flight (cntd)

Sir George Cayley separated forces of lift and drag.He knew that a flying machine would need somekind of propulsion to fly. He researched shapes with

less drag and investigated the cross section of atrout.

Francis H. Wenham constructed the first wind tunnelin 1871.

1889: Charles Renard predicted the necessaryamount of power for sustained flight.

1903: The Wright brothers flew the first poweredaircraft. (http://www.youtube.com/watch?v=uT2dQB_OgFE&feature=related)
http://www.youtube.com/watch?v=uT2dQB_OgFE&feature=relatedhttp://www.youtube.com/watch?v=uT2dQB_OgFE&feature=related


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The History of Flight (cntd x2)

Kutta-Joukowski condition(early 20th century)

described thecharacteristics of flow

around an airfoil. This

contributed to the creationof the Joukowski airfoil

which we use for airplanes

today.

QuickTime and aTIFF (Uncompressed) decompressor

are needed to see this picture.

www.viswiki.com/ en/Joukowsky_transform


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How Airplanes Fly

http://www.allstar.fiu.edu/aero/fltmidfly.htm


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Four main forces on an airplane: thrust, drag,lift, and weight.

Thrust and lift forces must be greater than

drag and weight forces for the plane to takeoff.

During level flight with constant speed, thenet force on the aircraft is zero. So,

thrust=drag and lift=weight.

How Airplanes Fly


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Lift

ksnn.larc.nasa.gov/ pokemon/unseen/main.html

Lift is generated when

the velocity of the fluid

over the wing is greater

than the velocity of the

fluid under the wing.

The higher the velocity,

the lower the pressureand the lower the

velocity, the higher the

pressure. Thus, thepressure under the wing

is greater than above,

generating LIFT!


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Thrust

Thrust is the force created by the engines tocounteract the drag force.

A propulsion system generates thrust byaccelerating a mass of gas: the thrust is in the

opposite direction from the gas.

In aircrafts, thrust is produced by propellers orjet engines.


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Drag

All parts of airplanes produce drag when the airplane is inmotion (the drag force is produced when there is adifference in velocity between fluid and object).

Drag is opposite to the direction of motion.

Similar to friction. The magnitude of force depends on the

properties of the surface material and the viscosity of thefluid.

Drag is caused by the shape of the body (shape alters thevelocity and pressure).

Induced drag is produced when the airplane generates lift.The magnitude depends on how much lift is created and theshape of the wing tips.


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Characteristics of Low Speed Aerodynamics

Low speed aerodynamics = subsonic aerodynamics.Sometimes are also called inviscid, incompressible, andirrotational.

Characterized by objects moving through fluids ofconstant density (incompressible). Only works if the fluidhas a low speed.

Subsonic aerodynamics have mach


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Sources of Information

http://en.wikipedia.org/wiki/Aerodynamics

http://www.grc.nasa.gov/WWW/K-12/airplane/thrust1.html

http://www.grc.nasa.gov/WWW/K-

12/airplane/drag1.html http://www.grc.nasa.gov/WWW/K-

12/airplane/mach.html

http://www.allstar.fiu.edu/aero/fltmidfly.htm

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