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High Speed
Aerodynamics
Jennifer McBethArul Suresh
COSMOS, Cluster 3
August 2, 2007Reference:
http://faculty.rmwc.edu/tmichalik/physmov.htm
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Brief History of High Speed Flight
World War II spurred interest in high speedaircraft
In 1940, the Bell aircraft company was
commissioned to build a research aircraft(X1) to try to reach & overcome the speed ofsound
US did not use wind tunnels, but Germanybuilt the first supersonic tunnel and used it forresearch
But on October 14, 1947, it was the X1 thatbecame the first aircraft to fly faster then thes eed of sound flown b Chuck Yea er
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Mach NumberThe ratio of the aircrafts speed to the speed
of sound When M
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Shock waves
Have large amplitude,at supersonicvelocity, characterizedby an amplitude-
dependent wavevelocity
Oblique shock wave:
Inclined at an obliqueangle to the direction ofairflow (as opposed toa normal shock wave
which is perpendicularto the direction of flow)Reference: www.wikipedia.org/wiki/Shock_wave
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Expansion fans
A region where thepressure is
decreasing and the
airflow isaccelerating
Occurs when a
supersonic airflowreaches an outside
corner and the
airflow expandsReference: www.wikipedia.org/wiki/Expansion_fan
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Forces on an Airplane
There are four major forcesacting on an airplane:
Weight Lift
Drag Thrust
Reference:
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Whats the difference at high
speed? At high speed, there is a new form of drag
The mechanism of lift also changes.
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Transonic Flight
Definition: Flight in which part of the flowover the airplane is supersonic;
characterized by a significant increase indrag and a decrease in lift
Normal shock
Possible boundary layer separationReference: http://www.stanford.edu/~jrdx/shock.html
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Boundary Layer Separation
Reference:http://selair.selkirk.bc.ca/aerodynamics1/High-
The vortex from the Vortex
Generator re-energizes the
boundary layer, preventing
flow separation
Flow separation would
cause a loss of lift and anincrease in drag (Parasite
Drag).
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These are the vortex generators on a Boeing 777wing.
Reference: http://web.lemoyne.edu/~hevern/2001trip/Aug4-5.html
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Supersonic flight
Flight in which the speed of the aircraftexceeds that of the speed of sound
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Supersonic Drag
Wave drag
Shock waves cause a discontinuity in the
characteristics of the air--the pressure
increases, and the velocity decreases. The
energy required to form shock waves
causes drag.
Force is now normal to the wing (instead of
normal to the flow), causing drag.
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Bow shock
If an airfoil with a round LE isused, then that causes an
area of stagnation, where the
air pressure is much higherthan the surroundings
This also takes energy, and the
pressure pushes back againstthe wing. To solve this, there
are few solutions.
Reference: waterocket.explorer.free.fr/images/bullet1.jpg
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Supersonic Lift
Airfoils: diamond, BI-elliptical
Increase sweep
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Airfoils
Reference:http://selair.selkirk.bc.ca/aerodynamics1/High-
Speed/default.htm
Low Speed Airfoil
High Speed Airfoil
Bi-convex Airfoil
Double Wedge Airfoil
Ideal Supersonic Airfoils
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The shock wave under the front of the wing
strengthens, and creates an area of higher
pressure under the front half of the wing.
The expansion fan on top strengthens, and
creates a low-pressure area over the back
half of the wing.
Lift is generated.
The center of pressure shifts back to ~50%chord.
At Positive Alpha
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Sweep
Reference:http://selair.selkirk.bc.ca/aerodynamics1/High-Speed/default.htm
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When air passes through an oblique
shock, the component perpendicular to
the shock is slowed to subsonic speeds
Therefore, if the wing is swept more than
the mach angle, then the air flowingperpendicularly to the wing is subsonic,
and so a subsonic airfoil can be used.
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Supersonic Propulsion
If a turbojet or turbofan is used atsupersonic speeds, the air entering the
jet intake needs to be subsonic, and
there are several ways to accomplishthis.
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Reference:http://selair.selkirk.bc.ca/aerodynamics1/High-
Speed/default.htm
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Reference:http://selair.selkirk.bc.ca/aerodynamics1/High-
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Center Body Diffuser
Reference:http://selair.selkirk.bc.ca/aerodynamics1/High-
Reference:http://selair selkirk bc ca/aerodynamics1/High Speed/default htm
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Reference:http://selair.selkirk.bc.ca/aerodynamics1/High-Speed/default.htm
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Conclusion
There are dramatic differences betweenlow speed and high speed flight
Transonic flight is flight near Mach 1
Supersonic flight is flight over Mach 1
Compressibility effects must be taken
into account.
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Bibliography http://selair.selkirk.bc.ca/aerodynamics1/High-Speed/default.htm
waterocket.explorer.free.fr/images/bullet1.jpg
http://history.nasa.gov/SP-4219/4219-060.jpg
http://web.lemoyne.edu/~hevern/2001trip/Aug4-5.html
http://www.stanford.edu/~jrdx/shock.html
http://quest.nasa.gov/aero/background
http://www.grc.nasa.gov/WWW/K-12/airplane/mach.html
http://faculty.rmwc.edu/tmichalik/physmov.htm
http://www.wikipedia.org/wiki/Expansion_fan
http://www.wikipedia.org/wiki/Shock_wave
http://selair.selkirk.bc.ca/aerodynamics1/High-Speed/default.htmhttp://waterocket.explorer.free.fr/images/bullet1.jpghttp://history.nasa.gov/SP-4219/4219-060.jpghttp://web.lemoyne.edu/~hevern/2001trip/Aug4-5.htmlhttp://www.stanford.edu/~jrdx/shock.htmlhttp://quest.nasa.gov/aero/backgroundhttp://www.grc.nasa.gov/WWW/K-12/airplane/mach.htmlhttp://faculty.rmwc.edu/tmichalik/physmov.htmhttp://www.wikipedia.org/wiki/Expansion_fanhttp://www.wikipedia.org/wiki/Shock_wavehttp://www.wikipedia.org/wiki/Shock_wavehttp://www.wikipedia.org/wiki/Expansion_fanhttp://faculty.rmwc.edu/tmichalik/physmov.htmhttp://www.grc.nasa.gov/WWW/K-12/airplane/mach.htmlhttp://quest.nasa.gov/aero/backgroundhttp://www.stanford.edu/~jrdx/shock.htmlhttp://web.lemoyne.edu/~hevern/2001trip/Aug4-5.htmlhttp://history.nasa.gov/SP-4219/4219-060.jpghttp://waterocket.explorer.free.fr/images/bullet1.jpghttp://selair.selkirk.bc.ca/aerodynamics1/High-Speed/default.htm8/6/2019 Vorticity and Potential Vorticity
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Acknowledgements
Professor Hafez
Mike Paskowitz
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