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AIRFOILS Shishir Damani Mechanical Engineering Department NIT - - PowerPoint PPT Presentation

Oct 02, 2022 535 likes •1.23k views

AE-705: Introduction to Flight AIRFOILS Shishir Damani Mechanical Engineering Department NIT Tiruchirappalli AE-705 Introduction to Flight Lecture 07 Capsule-04 OVERVIEW What is an Airfoil? Airfoil Terminologies and Nomenclature

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AE-705 Introduction to Flight Lecture 07 Capsule-04

AE-705: Introduction to Flight

AIRFOILS

Shishir Damani

Mechanical Engineering Department NIT Tiruchirappalli

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AE-705 Introduction to Flight Lecture 07 Capsule-04

OVERVIEW

 What is an Airfoil?  Airfoil Terminologies and Nomenclature  History of Airfoil  Types of Airfoils

 Flat Plate and Cambered Airfoil  Thick Airfoil  Laminar Airfoil  Low Reynolds Number Airfoil  Supersonic Airfoil  Supercritical Airfoil

 Modern Developments

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WHAT IS AN AIRFOIL?

Foil paper in air!!

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X section of the wing normal to span

Airfoil

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Airfoil Terminology

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AIRFOIL NOMENCLATURE

Airfoils belong to families too !

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NACA 4, 5, 6, 7 & 8 series SERI family Gottingen series Eppler family NASA family GAW series Clark family TsAGI family Lissaman series Lieback family Wortmann series Antonov family KFM series BAC family Beech series Bell family Boeing series RAF series

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 Solar Energy Research Institute  Advanced wind turbine blades

Source: Research paper on SERI Advance Wind Turbine Blades by J. Tangier, B. Smith, D. Jager

SERI NOMENCLATURE

Control peak rotor power (high winds) Produce power in Medium winds also

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 Devised ~ 50 years ago  Poor lift-to-drag ratio  Used in RC airplanes

KLINE FOGLEMAN AIRFOIL

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 Created at Gottingen University,Germany~1910s  There are one, two and three digit numbers

GOTTINGEN AIRFOIL

Source: http://www.aerospaceweb.org/question/airfoils/q0197.shtml

Gottingen 622 What’s the relation ??

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 Design based on conformal-mapping  Considered velocity distribution

EPPLER AIRFOIL

Source: https://en.wikipedia.org/wiki/Conformal_map#/ media/File:Conformal_map.svg

Function which preserves angles locally

For details: https://www.youtube.com /watch?v=woBgZMtiAeI

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AIRFOIL HISTORY

Who was behind all this??

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A VISIT TO THE PAST

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  • 1849 ; Gliders flown by Sir George Cayley
  • Scientific reasoning on cambered airfoil
  • 1884
  • Further studied and developed by Jean

Marie Le Bris, John J. Montgomery, Otto Lilienthal, Percy Pilcher, Octave Chanute and Augustus Moore Herring

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Sir George Cayley first glider

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 Lilienthal Ornithopter

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  • Wright Brothers developed three gliders
  • In July 1899 Wilbur tested wing warping
  • 1901 glider larger wing area

Stalled a few times Forward elevator

Source: https://en.wikipedia.org/wiki/Wright_brothers#Flights

Phewwww!!!

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Early WTT misleading!! Thin Airfoils WTT at low speed

At low speeds most flow remained attached but was separated in reality

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TYPES OF AIRFOILS

Let’s see what this has to give us??

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FLAT PLATE

Seriously!!!!!

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Flat Plates cannot produce Lift ?

WHY NOT USE FLAT PLATES?

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 Air flow speed and static pressure Lift  Camber changes V and P laminar flow  Most wings are designed with this concept 

η of the airfoil

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AE-705 Introduction to Flight Lecture 07 Capsule-04 Source: https://www.quora.com/Why-are-thick-airfoils-useful-Are-they-for-generating-lift-at-low-airspeeds

EFFECT OF CAMBER ON LIFT

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EFFECT OF CAMBER ON LIFT

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AE-705 Introduction to Flight Lecture 07 Capsule-04 Source: https://www.quora.com/Why-are-thick-airfoils-useful-Are-they-for-generating-lift-at-low-airspeeds

EFFECT OF CAMBER ON LIFT

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EFFECT OF CAMBER ON LIFT

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 Powerful engines Focus on L/D ratio ( L)  Drag aerodynamic characteristic

Source: https://www.quora.com/Why-are-thick-airfoils-useful-Are-they-for-generating-lift-at-low-airspeeds

EFFECT OF CAMBER ON LIFT

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THICK AIRFOILS

Are these stuffed up??

Source: https://backcountrypilot.org/forum/horizontal- stabilizer-shape-air-foil-vs-flat-pros-cons-18170

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 Thin airfoils stall at α  Separation of the flow over the top surface creates

drag loss of lift

Ludwig Prandtl (1875-1953)

I have a mathematical model

Larger LE radii Higher α before stall

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 Thicker airfoils flow separation till α

L

 German engineers planes climbed faster and

maneuver more sharply

Source: http://www.aviation-history.com/articles/great-war.htm

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Source: https://www.quora.com/How-can-wings-of-aircraft-store-fuel

 Thicker airfoils flow separation till α

L

 German engineers planes climbed faster and

maneuver more sharply

 Benefits; more space for:

  • Fuel tanks
  • Space for LG
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Source: https://www.quora.com/How-can-wings-of-aircraft-store-fuel

Source: http://www.clubhyper.com/reference/fw190landinggear_1.htm

 Thicker airfoils flow separation till α

L

 German engineers planes climbed faster and

maneuver more sharply

 Benefits; more space for:

  • Fuel tanks
  • Space for LG
  • Structural spar

Source: http://www.darkgovernment.com/RANCHO/CRASH/TWA/WINGBOX/wingbox.gif

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Some Airplanes with their Airfoils

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LAMINAR AIRFOIL

So they don’t have turbulence?

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Source: https://blog.rescale.com/leveraging-rescale-for-high-order-cfd-simulation/

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 Developed to fly faster  Aim: Maintain laminar flow over larger chord

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 Developed to fly faster  Aim: Maintain laminar flow over larger chord

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Turbulent flow on airfoil more stable?? Simple Answer: Skin friction drag compared to turbulent flow

WHY LAMINAR AIRFOILS?

P-51 Mustang

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Turbulent flow on airfoil more stable?? Simple Answer: Skin friction drag compared to turbulent flow

WHY LAMINAR AIRFOILS?

https://en.wikipedia.org/wiki/North_American_P-51_Mustang

P-51 Mustang

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LOW REYNOLDS NUMBER AIRFOIL

Fly at low speed….

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Reynolds number inertial effects vs viscous (fluid stickiness) effects

LRN AIRFOILS

Drag or stream wise resistance Limiting and controlling the maximum lift

Grumman HU-16B Albatross

Chord Reynolds Number = Vc/ν

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Reynolds number inertial effects vs viscous (fluid stickiness) effects

LRN AIRFOILS

Drag or stream wise resistance Limiting and controlling the maximum lift

Source: http://www.humanpoweredflying.propdesigner.co.uk/html/the_gossamers.html

Gossamer Albatross

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Reynolds number inertial effects vs viscous (fluid stickiness) effects

LRN AIRFOILS

Drag or stream wise resistance Limiting and controlling the maximum lift

Source: https://media.defense.gov/2005/Dec/26/2000574422/670/394/0/050322-F-1234P-028.JPG

Grumman HU-16B Albatross

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SUPERSONIC AIRFOIL

Faster than sound!!!

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Source: https://www.rt.com/usa/330524-sonic-boom-new-jersey/

Notice here

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 Engines (powerful) easy v( )  High speeds difficult for flow to remain attached

Sharp LE Do you notice something?

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Have you ever wondered that you could be flying on a plane producing shock waves?? Now what does that mean??

Video Courtesy: Russell Croman (https://www.youtube.com/watch?v=HekbC6Pl4_Y)

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 Objective: Delay the onset of wave drag  This aircraft speed is called the critical speed

Now hat does that mean??

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 Objective: Delay the onset of wave drag  This aircraft speed is called the critical speed

Source: https://www.nasa.gov/centers/armstrong/news/FactSheets/FS-044-DFRC.html

Large LE Radius Flat upper surface High cambered aft section

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 The flat upper surface does the  Reduces aerodynamic drag associated with

BL separation

Source: Richard Whitcomb; Review of NASA Supercritical Airfoils. NASA

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VERY LOW SPEED AIRFOIL

Do these fly at the speed of Maruti 800?

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 Lift with very less speed  Solar powered aircraft low power engines  The airfoil used on the Solar Challenger

VLS AIRFOILS

Source: http://www.aviastar.org/air/usa/maccready_solar.php

Flat upper surface for easy solar cells installation

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 Laminar airfoil was considered  NACA 63412 profile  Lissaman Hibbs 8025, 8230 and Wortmann

profiles also

Solar Impulse

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PARAFOIL

Used in parachutes?

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Source: https://www.gombergkites.com/inflated.html

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 Nonrigid (textile) airfoil inflated by the wind  Ram-air inflates it to a classic wing cross-

section

 Material-Ripstop nylon

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REFLEX AIRFOIL

Wow! Are these flexible?

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A flying wing is a tailless fixed-wing aircraft that has no definite fuselage

Source: Google images (B2 Bomber)

Non-symmetrical airfoils on flying wings

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Non-symmetrical airfoils on flying wings

S-Shape Lifted aft

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SYMMETRICAL AIRFOIL

Nature loves symmetry!!

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 Line of symmetry (chord)

Source: http://www.wbko.com/content/news/The-Latest-Missing-pilots-company-calls-it-a-difficult-day- 408890925.html

Pilatus PC-12

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 Line of symmetry (chord)  Best L/D ratio  Lower Cl than the asymmetrical airfoil  Tilting changes the flow of air Lift  Used on control surfaces

Source: http://www.wbko.com/content/news/The-Latest-Missing- pilots-company-calls-it-a-difficult-day-408890925.html

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INVERTED AIRFOIL

So we can fly upside down?

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 Usually for horizontal stabilizer  Provide –ve lift  downforce

Dornier 228

Source: https://planefinder.net/data/aircraft/G-SAYE

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THAT’S ALL !

Time for some self-study now