chapter 2 air and air flow
TRANSCRIPT
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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.