Bird s aerodynamics
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BIRD’S AERODYNAMICS. 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. . IMPORTANT TERMS. Essential for

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Bird s aerodynamics

Bird s aerodynamics


  • 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.

Important terms

Essential for

understanding their flight mechanism

  • Lift

  • Drag

  • Angle of attack

  • Stalling

  • Covert eddy flaps

  • Flapping

  • Take off and Landing

  • Camber

Bird s aerodynamics

  • 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

Bird s aerodynamics

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


  • 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


  • 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.


  • 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

Bird s aerodynamics

Bird s aerodynamics

Three major drag forces

  • Frictional drag(caused by friction of air and body surfaces).

  • Form drag

  • Lift -induced drag

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.

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.

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.


  • 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


  • 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

Bird s aerodynamics

  • 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

Types of wings

  • ELLIPTICAL WINGS-(short,rounded,for rapid take-offs)

  • HIGH ASPECT RATIO WINGS-(far longer than they are wide,for gliding )

Bird s aerodynamics

  • 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)


  • 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