Flapping Wing Aerodynamics Some Lessons from Natural Flyers Prof. - PowerPoint PPT Presentation

Flapping Wing Aerodynamics Some Lessons from Natural Flyers Prof. Rajkumar S. Pant AE-705 Introduction to Flight Lecture No. 19 Capsule 10

Aeronautical Technology v/s Natural Evolution AERONAUTICAL TECHNOLOGY NATURAL EVOLUTION  Fastest Aircraft: (SR-71 Blackbird )  Fastest Bird: Spine Tailed Swift  900 m/s = 32 body-lengths/s  47.5 m/s = 150 body-lengths/s  Fastest Roll Rate: A4 Skyhawk  Fastest Roll Rate: Barn Swallow  720 o /s  5000 o /s  Aircraft Highest g-rates = 7 – 9  Bird Highest g-rates 20 – 25 WHY ?  ~ 150 Million Years old  ~ 100 years old Humans fly commercially or recreationally, but birds fly professionally J . H. McMasters and M. J. Henderson, “Low speed single element airfoil synthesis ,” Technical Soaring , vol. 6, pp. 1 – 21, 1980. AE-705 Introduction to Flight Lecture No. 19 Capsule 10

Flapping Flight in Birds  Usually a Figure of Eight motion  Downward stroke, wing pronated , AoA ↓ Upward stroke, wing supinated , AoA ↑ The Dove by Ed Braverman   Three desirable f eatures of bird’s wing  Camber change and Twisting  Area expansion and contraction  Transverse bending  Similarities with Humans  Bone Structure  Muscle Structure AE-705 Introduction to Flight Lecture No. 19 Capsule 10 Source: http://www.cambridge.org/9781107037267 pp. 17

Wings: Aircraft v/s Birds Nachtigall, H. v. W. and J. Wieser (1966). "Profilmessungen am Taubenflugel." Zeit. PIGEON WING AIRCRAFT WING Vergl. Physiol. 52 : 333-346 Pigeon wings exhibit much higher change in Camber and Thickness along Span AE-705 Introduction to Flight Lecture No. 19 Capsule 10 Source: http://www.cambridge.org/9781107037267 pp. 18

Scaling Laws of Flying Bodies  The Great Flight Diagram AIRCRAFT  W/S v/s W v/s V 𝑋 1 𝑋 2 𝜍𝐷 𝑀 𝑊 2 , hence when  𝑇 = 𝑇 ↑, V ↑ 3 𝑋 𝑋 𝑇 = 𝑙 1  BIRDS o k 1 = 53 (Aircraft) o k 1 = 30.5 (Birds) INSECTS Source: T. Liu, “Comparative scaling of flapping - and fixed- wing flyers,” AIAA Journal , vol. 44, pp. 24 – 33, 2006. AE-705 Introduction to Flight Lecture No. 19 Capsule 10 Source: Tennekes H, The Simple Science of Flight from Insects to Jumbo Jets , Cambridge, MA, The MIT Press, 1996

Scaling of parameters with Mass m  Wingspan ( b)  b ~ 1 . 654 m 1 / 3 (aircraft) b ~ 1 . 704 m 1 / 3 (birds)  Wing Area ( s ) s ~ m 0.78 (most birds); s ~ m 1.04 (HB)  Large variations seen  Wing Flapping Frequency ( f wing )  Max. f wing ~ m ( - 1 / 3) Min. f wing ~ m ( - 1 / 6)  Larger Birds Flap slowly !  Wing Aspect Ratio ( AR )  Large soaring birds: AR ~ 15  L/D max ~ 20 AR ~ 30  L/D max ~ 60  Large Sailplanes: AE-705 Introduction to Flight Lecture No. 19 Capsule 10

Summary: Scaling of bird parameters with mass W PARAMETER UNITS SCALING W 1/3 Wingspan m m 2 W 2/3 Wing Area N/m 2 W 1/3 Wing Loading W 1/6 Min. Power W W 1/6 Speed for min. Power m/s W (-1/3) Max. Wing beat frequency /s W (-1/6) Min. Wing beat frequency /s AE-705 Introduction to Flight Lecture No. 19 Capsule 10

Fastest Flying Birds Level Flight (~ 171 kmph) Dive (~ 389 kmph) Spine Tailed Swift Peregrine Falcon AE-705 Introduction to Flight Lecture No. 19 Capsule 10

Mechanics of Gliding & Soaring  Gliding = Flights without Flapping  Thrust comes from Gravity  Glide Angle θ = 𝑀 𝐸 ) 1 ( 𝑀 𝐸 ↑, θ↓, Glide Range↑  As 𝑀 𝐸 ↑  As Size ↑ , Re ↑, o Albatross: b w = 3000 mm, L/D = 19 o Fruit Fly: b w = 6 mm, L/D = 1.8  Even Snakes can Glide !  Soaring Gliding Snakes  Gaining height due to thermals/updrafts AE-705 Introduction to Flight Lecture No. 19 Capsule 10

Improving glide characteristics by wing morphing 2𝑛𝑕 1 2 𝜍𝑇𝐷 𝑀 𝑊 2 = 𝑛𝑕 𝑑𝑝𝑡𝜄 ≈ 𝑛𝑕 ∴ 𝑊 ≈ 2𝑋  L = 𝑊 ≈ 𝜍𝑇 𝐷 𝑀 𝜍𝑇𝐷 𝑀  Assume C L = 0.65 and ρ = 1.2256 kg/m 2 Birds ↑ S as V glide ↓ 𝑋  V ∝ 𝑛 0.28 ∝ 𝑛 0.14 𝑇 ∝  Heavier birds glide at higher speeds Bird W/S V glide V glide % Error N/m 2 (Estim) m/s (Quoted) m/s Mute Swan 170 20.66 21 1.62 Albatross 140 18.75 19 1.33 Ultralight 133 18.27 18 -1.50 Graylag Goose 115 16.99 17 0.05 Common Gull 32 8.96 9 0.41 AE-705 Introduction to Flight Lecture No. 19 Capsule 10 Source: Tennekes H, The Simple Science of Flight from Insects to Jumbo Jets , Cambridge, MA, The MIT Press, 1996

Rotary Wing Aircraft & Natural Flyers : Similarities Rotary Wing Aircraft Natural Flyers  Lift  Lift Relative flow around rotors created by  Flapping wing about shoulder in an arc,  rotating continuously along central shaft and reversing every half cycle  Thrust  Thrust  Tilting the rotational plane of the rotor  Tilting the flapping stroke plane forward o down and forward on the downstroke o up and backward on the upstroke  During Forward Flight  During Forward Flight  Make the stroke more vertical by increasing the up-and-down amplitude  Change the angle of the rotors AE-705 Introduction to Flight Lecture No. 19 Capsule 10

Wingtip paths relative to the body BOW FLY ALBATROSS PIGEON LOCUST HORSESHOE BAT BEETLE FRUITFLY  Smaller flyers flap in a more complex pattern AE-705 Introduction to Flight Lecture No. 19 Capsule 10

Flapping Patterns of some Natural Flyers Canada Goose Fruit Bat Hummingbird Hawk Moth Source: http://www.coolinfographics.com/blog/2015/4/27/flight-patterns-deconstructed.html AE-705 Introduction to Flight Lecture No. 19 Capsule 10 Dragon Fly

Flapping in Slow Motion PIGOENS DRAGON FLY FRUIT BATS AE-705 Introduction to Flight Lecture No. 19 Capsule 10

Hovering Flight AE-705 Introduction to Flight Lecture No. 19 Capsule 10 Humming Birds in slow motion

Principal Sources 1. Shyy et al., An Introduction to Flapping Wing Aerodynamics, Cambridge Aerospace Series, ISBN 9781107037267, 2013. 2. Tennekes H., The Simple Science of Flight from Insects to Jumbo Jets, Cambridge, MA, The MIT Press, 1996. AE-705 Introduction to Flight Lecture No. 19 Capsule 10