Drag And Its Reduction Siddharth Joshi Mechanical Engg. Deptt. VIT - - PowerPoint PPT Presentation

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Drag And Its Reduction Siddharth Joshi Mechanical Engg. Deptt. VIT - - PowerPoint PPT Presentation

Jun 12, 2023 228 likes •840 views

AE-705: Introduction to Flight Drag And Its Reduction Siddharth Joshi Mechanical Engg. Deptt. VIT Vellore AE-705 Introduction to Flight Lecture-10 Capsule-05 Source: https://upload.wikimedia.org/wikipedia/commons/4/4a/George_Cayley2.jpg SIR

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AE-705 Introduction to Flight Capsule-05 Lecture-10

AE-705: Introduction to Flight

Drag And Its Reduction

Siddharth Joshi

Mechanical Engg. Deptt. VIT Vellore

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AE-705 Introduction to Flight Capsule-05 Lecture-10

INTRODUCTION TO DRAG

Source: https://upload.wikimedia.org/wikipedia/commons/4/4a/George_Cayley2.jpg

SIR GEORGE CAYLEY (1773 – 1857)

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AE-705 Introduction to Flight Capsule-05 Lecture-10

DRAG

Force opposing motion of Aircraft Drag generated due to ΔV

ΔV= Vsolidobject - Vfluid

If ΔV=0 ↔ No motion between solid and fluid ↔ No Drag

Source: https://s-media-cache-ak0.pinimg.com/originals/51/42/b3/5142b32c3fedf745c39ce11aa16be27d.gif

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AE-705 Introduction to Flight Capsule-05 Lecture-10

Thrust Drag Airflow

Source: https://encrypted-tbn0.gstatic.com/images?q=tbn:ANd9GcQO0LNN_VHhty3cDXpBKBa3Nd4FTA55BsbpLdfa8pVO3Dxo1ghz

Drag // direction of the free-stream velocity of the airflow

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AE-705 Introduction to Flight Capsule-05 Lecture-10

Thrust > Drag

Source: https://tenor.com/view/batman-airplane-gif-5249888 Source: http://www.dccomics.com/sites/default/files/video/THE_LEGO_BATMAN_MOVIE_TRAILER_2_thumb_56f9a68c4f62a0.07314395.jpg

Drag must be overcome by Thrust in order to achieve forward motion

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AE-705 Introduction to Flight Capsule-05 Lecture-10

Source: https://i1.wp.com/cdn.makezine.com/uploads/2014/01/aeronautics.png

Source: http://cdn.toonvectors.com/images/35/122772/toonvectors-122772-940.jpg

But who was the first person to

  • bserve

Drag?

George Cayley [1773-1857]

Father of Aviation Identified the four forces- Weight Lift Drag Thrust

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AE-705 Introduction to Flight Capsule-05 Lecture-10

Cayley’s Whirling Arm Apparatus

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AE-705 Introduction to Flight Capsule-05 Lecture-10

Cayley’s Boy Carrier, 1849

  • J. A. D. Ackroyd, Sir George Cayley: The Invention of the Aeroplane near Scarborough at the Time of Trafalgar,

Journal of Aeronautical History Paper No. 2011/ 6130

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AE-705 Introduction to Flight Capsule-05 Lecture-10

Cayley’s Governable Parachute, 1852

Original Drawing 1852 Full Scale Replica 1974

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AE-705 Introduction to Flight Capsule-05 Lecture-10

 Please, Sir George, I wish to give notice, I

was hired to drive and not to fly !

The Reluctant Airman

 John Appleby

  • Cayley’s Coachman

 First manned flight

  • n an HTA aircraft

 ~ 153 m  Brompton-by-

Sawdon, near Scarborough, UK

Scene from Anglia TV Ltd, series "On The Wing“, 1974

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AE-705 Introduction to Flight Capsule-05 Lecture-10

Full Scale replica flown by Derek Piggot in 1972

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AE-705 Introduction to Flight Capsule-05 Lecture-10

Sir George Cayley : Summing Up

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AE-705 Introduction to Flight Capsule-05 Lecture-10

COMPONENTS OF DRAG

Breaking Drag down to bits and pieces !

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AE-705 Introduction to Flight Capsule-05 Lecture-10

Drag= Profile Drag + Induced Dag + Wave Drag

Pressure Drag + Skin Friction Drag

Also called Form Drag Laminar or Turbulent

Profile Drag independent

  • f lift

Also called Parasite Drag

Additional Profile Drag due to lift

Should be small at cruise

Due to lift generated vorticity shed into wake

Supersonic

Drag due to generation of shock waves

Wave drag due to lift Wave drag due to volume

Drag due to lift Zero lift Drag Zero lift Drag

Subsonic

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AE-705 Introduction to Flight Capsule-05 Lecture-10

INDUCED DRAG

Source: http://howthingsfly.si.edu/sites/default/files/image-large/il_wingtipvortexedit_lg.jpg

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AE-705 Introduction to Flight Capsule-05 Lecture-10

Source: http://cdn.toonvectors.com/images/35/122772/toonvectors-122772-940.jpg

Lets see how Induced Drag is generated

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AE-705 Introduction to Flight Capsule-05 Lecture-10

Source: http://cdn-image.travelandleisure.com/sites/default/files/styles/1600x1000/public/delta0315-party-plane.jpg?itok=BgvL7aan

Total Force Vertical component → Lift Total Force Horizontal Component → Induced Drag

Relative Wind Total Force Induced Drag Weight Lift Thrust

Total aerodynamic force generated by the wing is tilted backwards

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AE-705 Introduction to Flight Capsule-05 Lecture-10

Drag created due to the vortices at the tip of the aircraft's wing

Source: https://upload.wikimedia.org/wikipedia/commons/6/68/US_Navy_110606-N-DR144-314_An_F-A-18E_Super_Hornet_assigned_to_Strike_Fighter_Squadron_%28VFA%29_81_maneuvers_over_the_Nimitz-class_aircraft_carrier_US.jpg

Airflow at the tips of the wings to curl around in a circular motion

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AE-705 Introduction to Flight Capsule-05 Lecture-10

EXPRESSION FOR INDUCED DRAG

Di = 1 2 ρ0Ve

2SCDi

Source: https://upload.wikimedia.org/wikipedia/en/3/39/Induce_drag_downwash.png

CDi = kCL

2

π𝐁𝐒 CL = L 1 2 ρ0Ve

2S

Di = kL2 1 2 ρ0Ve

2Sπ𝐁𝐒 Aspect Ratio Wing Area Lift Air Density Equivalent Airspeed

&

Induced Drag

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AE-705 Introduction to Flight Capsule-05 Lecture-10

FACTORS AFFECTING INDUCED DRAG

  • 1. Angle of Attack
  • 2. Airspeed
  • 3. Aspect Ratio

Source: http://aeroscholars.com/multimedia/img/airspeed_indicator.gif

Source: http://www.pilotwings.org/uploads/2/1/9/3/21932436/8536864.jpg?461

α

Relative Wind →

Low Aspect Ratio wings High Aspect Ratio wings

Source: https://www.skybrary.aero/images/thumb/AoA.jpg/400px-AoA.jpg

NEXT

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Lift ↑ ↔ Induced Drag ↑ ↔ Angle of Attack ↑ Lift and Induced drag ↑ with Angle of Attack upto the critical angle (stall takes place) BACK

Source: http://studysoaring.stlsoar.org/clvsaoa.gif

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CL ↑ ↔ Induced Drag ↑ ↔ Airspeed ↓ Low speed ↔ Angle of Attack ↑ ↔ Drag ↑ High speed ↔ Angle of Attack ↓ ↔ Drag ↓

Di = kL2 1 2 ρ0Ve

2Sπ𝐁𝐒

Source: http://www.pilotwings.org/uploads/2/1/9/3/21932436/1042520.jpg?426

Di ↔ 1 Ve

2

BACK

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AE-705 Introduction to Flight Capsule-05 Lecture-10

Induced Drag ↑ ↔ Aspect Ratio ↓ Aspect Ratio ↑ ↔ Thinner Wing ↔ Smaller wing vortices ↔ Induced Drag ↓

Source: https://www.youtube.com/watch?v=JMjUxn2cqSI

BACK

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AE-705 Introduction to Flight Capsule-05 Lecture-10

Increasing Aspect Ratio

Longer span wing ↔ higher aspect ratio ↔ less induced drag

Boeing B-52

Limitation: Thin long wing requires a large structural weight to support it

Source: http://www.aerospaceweb.org/aircraft/bomber/b52/b52_21.jpg Source: http://cdn.toonvectors.com/images/35/122772/toonvectors-122772-940.jpg

Lets see a High Aspect Ratio RC Plane

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AE-705 Introduction to Flight Capsule-05 Lecture-10

Tip Plates Inhibit the formation of tip vortices

Source: https://upload.wikimedia.org/wikipedia/commons/thumb/e/e0/Grob_G103C_Glider.jpg/1280px-Grob_G103C_Glider.jpg

Source: http://www.derbyaeroclub.com/Pictures/bory.JPG

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Winglets

Reduces the strength of wingtip vortices

Source: http://www.pilotwings.org/uploads/2/1/9/3/21932436/5770030.jpg?334

Converts some of the otherwise-wasted energy in the wingtip vortex to thrust

Source: https://upload.wikimedia.org/wikipedia/commons/thumb/5/5a/Winglet_B737-800.JPG/220px-Winglet_B737-800.JPG Source: http://cdn.toonvectors.com/images/35/122772/toonvectors-122772-940.jpg

Lets see how Winglets work

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Wing Grid

Source: http://www.reaa.ru/yabbfiles/Attachments/1041849_003.jpg

  • 60% ↓ Dinduced compared to

conventional wings

  • Increased resistance to tip stall
  • Increased overall lift

Source: http://cdn.toonvectors.com/images/35/122772/toonvectors-122772-940.jpg

But why are Wing Grids used?

Source: http://www.allstar.fiu.edu/aero/images/Uhuseitehinten175.jpg

Source: http://www.allstar.fiu.edu/aero/winggrid2.html
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Spiroids

Eliminate concentrated wingtip vortices

Source: https://upload.wikimedia.org/wikipedia/commons/b/b2/Spiroid_winglet.jpg

Source: http://airpigz.com/blog/2010/8/27/poll-spiroids-funky-circular-winglets-love-em-or-hate-em.html
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REDUCING PARASITE DRAG

Source: https://www.youtube.com/watch?v=WTTKFqm20RY

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AE-705 Introduction to Flight Capsule-05 Lecture-10

PARASITE DRAG

Produced by objects that disrupt the air flow PARASITE DRAG

Form Drag Skin Friction Drag Interference Drag

Source: http://www.pilotwings.org/uploads/2/1/9/3/21932436/1563066.jpg?341

Source: http://aeronotes.weebly.com/uploads/2/5/3/7/25370889/7808429.gif?368

Source: http://www.boldmethod.com/images/learn-to-fly/aerodynamics/parasite-drag-and-your-airplane/skin-friction-drag.jpg
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Parasite Drag ↑ ↔ Airspeed ↑

Source: http://www.pilotwings.org/uploads/2/1/9/3/21932436/5904046.jpg?443

At high speeds ↔ Parasitic Drag > Induced Drag At Low speeds ↔ Induced Drag > Parasite Drag

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FORM DRAG

Created by objects deflecting and disrupting air flow

Source: http://cdn.toonvectors.com/images/35/122772/toonvectors-122772-940.jpg

Objects such as?

Source: https://s-media-cache-ak0.pinimg.com/originals/f1/8f/e4/f18fe4647d0b58e3df0fa7f5b3ee175c.jpg

Landing Gear

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AE-705 Introduction to Flight Capsule-05 Lecture-10

FORM DRAG

Source: http://cdn.toonvectors.com/images/35/122772/toonvectors-122772-940.jpg

Objects such as?

Source: https://i.stack.imgur.com/3KB80.jpg

Antenna

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AE-705 Introduction to Flight Capsule-05 Lecture-10

FORM DRAG

Source: http://cdn.toonvectors.com/images/35/122772/toonvectors-122772-940.jpg

Objects such as?

Source: https://upload.wikimedia.org/wikipedia/commons/thumb/2/26/Wing_Brace_strut.JPG/1280px-Wing_Brace_strut.JPG

Wing Struts

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AE-705 Introduction to Flight Capsule-05 Lecture-10

FORM DRAG

Laminar flow

Source: http://www.pilotwings.org/uploads/2/1/9/3/21932436/5565432.jpg?264

Disruption by Object

Turbulent Flow

Air

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AE-705 Introduction to Flight Capsule-05 Lecture-10

Application: Spoilers → Helps the plane to slow down

FORM DRAG

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AE-705 Introduction to Flight Capsule-05 Lecture-10

FORM DRAG

Cross sectional Area ↑ ↔ Form Drag ↑

Boeing 747 F-16 Cessna 172

Form Drag decreases

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AE-705 Introduction to Flight Capsule-05 Lecture-10

SKIN FRICTION DRAG

Created by the movement of air flow near the skin of the aircraft

Source: http://cdn.toonvectors.com/images/35/122772/toonvectors-122772-940.jpg

But what causes skin friction drag?

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AE-705 Introduction to Flight Capsule-05 Lecture-10

SKIN FRICTION DRAG

𝐃𝐠 = 𝛖𝐱 𝐫

Skin friction coefficient Cf

Shear stress Dynamic pressure

Cf varies with

  • Reynolds number
  • Mach number
  • Character of the boundary layer
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INTERFERENCE DRAG

Generated by mixing of airflow streamlines between airframe components

Source: http://learntoflyblog.com/wp-content/uploads/2016/04/4-6-768x575.png

Wing and Fuselage intersection

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Intersection of airstreams creates eddy currents and turbulence

INTERFERENCE DRAG

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AE-705 Introduction to Flight Capsule-05 Lecture-10

INTERFERENCE DRAG

Smaller Angle ↔ Interference Drag ↑

Source: http://www.boldmethod.com/images/learn-to-fly/aerodynamics/how-interference-drag-affects-your-airplane-performance/angles-interference-drag.jpg
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Reduction of Parasite Drag

Streamlining

Contouring of the aircraft’s body to reduce drag

Source: http://www.flyingmag.com/sites/flyingmag.com/files/styles/medium_1x_/public/import/2014/sites/all/files/_images/201404/Lancair-gear.jpg?itok=UfG_seJu

Lancair Evolution Landing Gear

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Reduction of Parasite Drag

Streamlining

Contouring of the aircraft’s body to reduce drag

Source: http://mthobby.pcperfect.com/ch601/Cowling_model.bmp

CH601 Cowling

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Reduction of Parasite Drag

Streamlining

Contouring of the aircraft’s body to reduce drag

Source: http://www.zenithair.com/zodiac/607/ph-zen.jpg

Zodiac XL Tail Dragger

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AE-705 Introduction to Flight Capsule-05 Lecture-10

Reduction of Parasite Drag

Streamlining

Contouring of the aircraft’s body to reduce drag

Source: https://i.stack.imgur.com/HtsVp.jpg

Boeing 787 Engine Nacelle

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AE-705 Introduction to Flight Capsule-05 Lecture-10

Fairings

Act as covers for gaps and spaces between parts of an aircraft to reduce interference drag

Source: http://www.boldmethod.com/images/learn-to-fly/aerodynamics/how-interference-drag-affects-your-airplane-performance/fairings-wing.jpg
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Fairings

Act as covers for gaps and spaces between parts of an aircraft to reduce interference drag

Source: http://www.zenithair.com/zodiac/607/601-ul-td.jpg

Landing Gear Fairings

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Fairings

Act as covers for gaps and spaces between parts of an aircraft to reduce interference drag

Source: https://upload.wikimedia.org/wikipedia/commons/8/87/Ba_b757-200_g-bpei_closeup_arp.jpg

Boeing 757 Flap Track Farings

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Tail Cones

Source: http://www.cap-ny153.org/Fairing%20Tail%20Cone.jpg

Reduces the form drag of the fuselage

Source: http://www.cap-ny153.org/Fairing%20Tail%20Cone%202.jpg

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AE-705 Introduction to Flight Capsule-05 Lecture-10

Tail Cones

Source: http://www.cap-ny153.org/Fairing%20Tail%20Cone.jpg

Reduces the form drag of the fuselage

Source: http://www.cap-ny153.org/Fairing%20Tail%20Cone%202.jpg

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Smart Vortex Generator (SVG)

Devices to delay or prevent flow separation SVGs change their shape autonomously Take off → vortex-generating position During Flight → drag reduction position

Source: https://image.slidesharecdn.com/windpowerengineering-vortexgeneratorsonwindturbineswebinar-151005235800-lva1-app6891/95/windpower-engineering-webinar-vortex-generators-on-wind-turbines-8-638.jpg?cb=1444089612

Vortex Generators

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Joint Wings

Source: http://aero.stanford.edu/reports/nonplanarwings/JWConcept.jpg

Thinner, smaller chord and higher aspect ratio wings

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AE-705 Introduction to Flight Capsule-05 Lecture-10

Strut Braced Wings

Source: https://www.researchgate.net/profile/Eli_Livne/publication/256186912/figure/fig20/AS:392583424561154@1470610590070/Figure-44-Key-elements-of-the-2011-Strut-Braced-Wing-concept-UAV.jpg

Badly designed struts can cause massive interference Significant reductions in both vortex and wave drag

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Blended Wing Concept Reduction of boundary layer separation regions

Blended Wing Body (BWB) Aircraft

Source: http://i.dailymail.co.uk/i/pix/2016/09/12/16/383F15A900000578-3785673-image-m-2_1473694784931.jpg

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WAVE DRAG

Source: https://media.tenor.com/images/a14b376bb5e882cb6db2d32aaa45e272/tenor.gif

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Wave Drag

Drag generated by shock waves Occurs at transonic and supersonic speeds

Shock Wave Airflow separation causing wave drag

Source: http://www.boldmethod.com/images/learn-to-fly/aerodynamics/wing-sweep/wave-drag.jpg Source: http://bestanimations.com/Military/Planes/jet-fighter-military-plane-animated-gif-4.gif

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Wave Drag Reduction

Swept Wings Backward/Forward angled wings Delays Shock waves and reduces drag

Source: http://www.military-today.com/aircraft/tupolev_tu160_blackjack.jpg

Tupolev Tu-160

Source: http://cdn.toonvectors.com/images/35/122772/toonvectors-122772-940.jpg

Here’s a Swept wing in action

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Küchemann Carrots

Source: http://i1285.photobucket.com/albums/a585/hotelalpha200/1040796_zpsgb5ev0vu.jpg

Anti shock body → reduces wave drag at transonic speeds

Convair 990 Coronado

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NEXT CLASS: FRIDAY 8 SEP

Tutorial and Quiz for Capsule-05