aeronautics 1110x 3b-slides
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Aeronautics 1110x 3b-slidesTRANSCRIPT
Ir. Jos Sinke
Li#
Introduc)on to Aeronau)cal Engineering
Cyron -‐ CC -‐ BY
Li# equa)on
J. Scavini -‐ CC -‐ BY -‐ SA
LLi7 is given by:
Li# equa)on
J. Scavini -‐ CC -‐ BY -‐ SA
LLi7 is given by:
What is the unit of CL?
Li# coefficient
-‐ The ‘efficiency’ of the airfoil in generaFng li7 -‐ Depends on airfoil & angle of aKack
Airfoils
NACA airfoil nota)on
Leading edge (LE)
Thickness Camber Trailing edge (TE)
Chord line Chord c
Mean camber line
NACA 2412 means: -‐ 2% camber (of chord length) -‐ At 0.4 of the chord (from LE) -‐ And 12% thickness/chord raFo
Other li# parameters
Wing surface area S -‐ A design parameter Velocity V -‐ A design parameter Air density ρ -‐ Depends on alFtude & temperature
Revedavion.com -‐ CC -‐ BY -‐ NC -‐ SA
Where does li# come from?
Bernoulli’s law: “Sum of sta)c and dynamic pressure is constant” Higher velocity mean lower pressure! So li# by pressure difference
V VV
p pp
Airfoil li#
High pressure
Low pressure L
D
Velocity change Pressure distribu)on Li# & Drag
Try yourself: NASA Foilsim
Velocity measurement
QuesFon: Can we use Bernoulli’s law to measure speed? We measure airspeed
ptot -‐ ps
ptot
ps
ps
Pitot tube
Li# curve
CL [-‐]
α [°]
CLmax
α
Take-‐off and landing
-‐ What to do if we want to fly at low speeds?
-‐ W does not change -‐ If V should decrease, CL and/or S should increase -‐ Devices to do both! Y. Yosiaki -‐ CC -‐ BY -‐ SA
High li# devices
Aceebee -‐ CC -‐ BY -‐ NC -‐ SA
Flaps
Slats
High li# devices
Purpose: Fly at low speeds By: Increasing criFcal
Increasing Increasing wing area S
Slats: Flaps:
Slats Flaps CL [-‐]
α [°]
NiD.29 -‐ CC -‐ BY -‐ SA
Wing geometry
Wing span Wing surface area Root chord Tip chord Taper (=ct/cr) Sweep angle
D. Busiak -‐ CC -‐ BY -‐ NC -‐ ND
Sb
ct Λ
cr
Li#
M. Visser -‐ CC -‐ BY -‐ SA