Chapter 2 Air and Air Flow

8/19/2019 Chapter 2 Air and Air Flow

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Air and Airflow


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Air Resistance or DRAG


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Effect of Streamlining


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Air Resistance : Drag in aviation;

Reduce as much as possible.

Drag : Is due to FOR !pressure"

and #$I% !surface"

FOR : In front high pressure!Flat &late" !above normal"

Reduced pressure

!below normal" behind.Flow bifurcates in front'

A stagnation point of

highest pressure and

no movement.


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#treamlines : (ines showing the

direction of flow of afluid at an) particular

moment.

#ucceeding molecules

follow the same path.

#treamlined #hape : inimum

resistance'Fineness Ratio of * to +'

a,imum thic-ness at

about /* rd distance


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#-in Friction : Due to viscosit)'

Air at surface is

brought to almoststand still.

Gradual increase tillfree air speed.

Increases with

increase in speed


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0oundar) (a)er : (a)er in which this

change in speed occurs

1hic-ness' more in turbulent la)er

(aminar Flow : One molecule follows

another

1urbulent Flow : 2apha3ard' more energ)'

1ransition &oint : 4here flow changes

from laminar to turbulent.

oves forward with

increase in speed


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0ernoulli5s : & 6 78 6 g3 9 onstant

4here & is pressure' = is densit)'

7 is velocit)' g is gravit) constant

and 3 is change in height

If change in height is negligible'

g3 can be ignored.

1hen & 6 ?=78 9 onstant

& is #tatic and ?=78 is D)namic pressure


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#tagnation pressure 9

#tatic pressure 6

D)namic pressure


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Resistance : #hape of the bod)

Depends on Frontal area of the bod)

#


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R(A1IO%#2I& 014%

AIR#&D#

• Indicated Airspeed !IA#". ASI (Pressure

Gauge)

• 1rue Airspeed !1A#". Corrected for

Density error as well.

• Ground #peed !G#". TAS corrected for

local winds.

Chapter 2 Air and Air Flow

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