Lift Introduction to Aeronautical Engineering Ir. Jos Sinke Cyron - - PowerPoint PPT Presentation

• Ir. Jos Sinke

Lift

Introduction to Aeronautical Engineering

Cyron - CC - BY

Lift equation

• J. Scavini - CC - BY - SA

L

Lift is given by:

Lift equation

• J. Scavini - CC - BY - SA

L

Lift is given by: What is the unit of CL?

Lift coefficient

• The ‘efficiency’ of the airfoil in generating lift
• Depends on airfoil & angle of attack

Airfoils

NACA airfoil notation

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 ratio

Other lift parameters

Wing surface area S - A design parameter Velocity V - A design parameter Air density ρ - Depends on altitude & temperature

Revedavion.com - CC - BY - NC - SA

Where does lift come from?

Bernoulli’s law: “Sum of static and dynamic pressure is constant” Higher velocity mean lower pressure! So lift by pressure difference

V V

V

p

p p

Airfoil lift

High pressure Low pressure

L D Velocity change Pressure distribution Lift & Drag

Try yourself: NASA Foilsim

Velocity measurement

Question: Can we use Bernoulli’s law to measure speed? We measure airspeed

ptot - ps

ptot ps ps

Pitot tube

Lift curve

CL [-] α [°] CLmax 

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

Dmitry Terekhov CC - BY - SA

Flaps Slats

High lift devices

High lift devices

Purpose: Fly at low speeds By: Increasing critical 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

S b ct Λ cr

Lift

• M. Visser - CC - BY - SA