1. BIRD’S AERODYNAMICS

2. ABSTRACT Man has always dreamed of being able to fly.
Our long years of experiment and research have resulted in machine with advanced technologies.
However our techniques are really primitive as compared to nature’s flying machine.

3. IMPORTANT TERMS Essential for understanding their flight mechanism
Lift
Drag
Angle of attack
Stalling
Covert eddy flaps
Flapping
Take off and Landing
Camber

4. LIFT Due to difference in pressures in upper and lower surface of wing
Upper surface of air deflects the air downwards
Airflow follows the tilted wing,sticks to surface, called COANDA EFFECT

5. Lift increases with increase in angle of attack
Difference in pressures creates lift
Air above the wing moves faster ,creating low pressure above ,hence creating lift
Lift increases with increase in angle of attack

6. ANGLE OF ATTACK
Angle between reference line of lifting boy and incoming air flow
Also called as angle of incidence
Coefficient of lift increases with increase in angle of attack upto critical angle of attack
After critical angle of attack,STALLING occurs

7. STALL
After critical angle of incidence is attained,flow separates of the wing,causing less lift.
Stalling occurs generally during beginning of flight or at slow speeds
Slower moving air may not move smoothly over the wing
Airflow above the wing becomes turbulent

8. ALULA Thumb shaped,also called as ‘COVERTS’.
Eddy developed starts from trailing edge to leading edge
‘COVERT EDDY FLAPS’ prevent eddy to reach to leading edge
Help maintain lift at low speeds,prevent STALL.

9. FLAPPING Flapping in such a way so as to create both THRUST and LIFT.
THRUST counteracts DRAG, LIFT counteracts WEIGHT.
Flapping involves two stages: downstroke and upstroke
Downstroke causes majority of lift and thrust

10. Upstroke also causes some lift, depending upon shape of wing
During upstroke wing is folded slightly inwards to reduce friction
Angle of attack increases during downstroke,while decreases during upstroke

11. DRAG Three major drag forces
Frictional drag(caused by friction of air and body surfaces).
Form drag
Lift -induced drag

12. FORM DRAG Arises because of form of object.
Larger apparent cross-section area will have larger drag than thinner bodies.
Sleek design or design that are streamlined are critical for achieving minimum drag.
Form drag increases with increase in air speed. e

13. LIFT INDUCED DRAG
Occurs whenever a moving object redirects the airflow coming at it.
Induced drag increases with increase in angle of attack.
Induced drag decreases with increase in air speed.

14. TAKE-OFF Most energetically demanding aspects of flight.
Large birds like albatrosses need to run up in order to generate airflow to take off
Small birds can do so by taking a jump
PECTORA muscle provides about 95% of strength required for flight.

15. LANDING Problem for large birds with high wing loadings
Landing on water is simpler,using their feet as skids
Certain birds aim at intended landing area and pull up before hand
Large birds like geese involve in rapid alternating series of sideslips called WHIFFLING

16. CAMBER Symmetry between top and bottom curves of an airfoil
Symmetric airfoils( with zero camber) generate no lift at zero angle of attack.
Generally upper camber of an airfoil is greater than lower camber.
Supersonic flights use supercritical airfoil;one with negative camber

17. When camber is increased beyond a limit,STALLING occurs
Even if angle of attack is zero,airflow above the upper surface can be separated due to excessive cambering
Idea of cambering helps designing aircraft wings

18. TYPES OF WINGS ELLIPTICAL WINGS-(short,rounded,for rapid take-offs)
HIGH ASPECT RATIO WINGS-(far longer than they are wide,for gliding )

19. HIGH SPEED WINGS-(short,pointed,for high speeds)
SOARING WINGS WITH DEEP SLOTS-(shorter size of wings helps in take-off,slots at tips of wings prevent induced drag)

20. HOVERING Done by birds with high aspect ratio wings
Humming birds are exception as they create lift in both upstroke and downstroke
Generally small birds hover, but some larger birds do so by flying in headwind