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Vorticity and Potential Vorticity

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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.htm
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    Acknowledgements

    Professor Hafez

    Mike Paskowitz


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