airfoils and wings

8/9/2019 Airfoils and Wings

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Airfoils and wings

Elements of aeronautics


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People not interested, plz bequiet


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Airfoil Cross section shape obtained by the

intersection of wing with the planeperpendicular is called airfoil


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Design features of airfoil

• Chord length

• Center of pressure

•

Maximum thicness• Angle of attac

• Camber

•

Aerodynamic center• Mean camber line


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Mean camberline

Mean camberline

!which is thelocus of points

halfway

between theupper and lower

surfaces as

measuredperpendicular tothe mean

camber itself


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Methods to "nd camber and max thicness

#$di%ide the airfoil into #& equal segments

'$the longest of the segments then gi%e the thicness of the pro"le

and locus of their centers is de"ned as mean caber line

($another possibility is to de"ne the mean camber line as the locus of the center of the circles inscribed to the pro"le


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Chord length

• The chord of anairfoil is an imaginarystraight line drawn

through the airfoilfrom its leading edgeto its trailing edge$


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Camber

Maximum distance between meancamber line and chord line, measured

perpendicular to the chord line


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Maximum thicness

Maximum thicness of theairfoil is the maximum

distance

from the bottom edge to the


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Angle of attac

Angle between chord line and

relati%e wind is called angle ofattac


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Aerodynamic center


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Aerodynamic center#$ )# is the resultant force due to the

upper surface pressure distribution

'$)' is the resultant force due to thelower surface pressure distribution$

($ if )'*)#, lift is produced$

+$this force will create a moment


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Point at which the resultant force

acts

• )or each angle of attac,pressure distribution o%er theairfoil will %ary

• hus the point at which resultant

acts also changes• he point at which resultant acts

is center of pressure

• Center of pressure is the a%eragelocation of the pressure

•

he procedure for "nding thecenter of pressure point is similarto the procedure for "nding thecentroid in a cross section$


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Aerodynamic center

• -o for change in each and e%eryangle of attac, the center ofpressure will change and it will

induce a moment with a referencepoint$

• .t is found experimentally and

analytically hat if force is applied/#0+1th of chord from the leadingedge, the aerodynamic moment

remains constant for %arious angle of


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• 2elocity of air farupstream of anairfoil is called free

stream %elocity

• Direction of freestream %elocity is

called relati%ewind


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3ift and drag

• Aerodynamic forceacting perpendicularto the relati%e wind4

lift

• Aerodynamic forceacting parallel to the

relati%e wind4drag


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)inding lift force

• 3ift is a function of followingparameter – )ree stream %elocity

– Density at the altitude

– 5ing area

– Angle of attac

– -hape of the airfoil – 2iscous e6ect

– compressibility


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)inding lift

• -ince lift force dependent of many%ariable$it is hard to get accurateresults with the help of wind

tunnel/ time constraint, largecollection of data1

• -o lift force is found by dimensional

analysis/77 study1


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Drag and moment force


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Airfoil designation

• 8ACA/national ad%isory committee for aeronautics,formerly 8A-A1 systematically in%estigated the e6ectof %arious airfoil parameter on aerodynamic beha%ior$

• 9A-ED :8 CAM9E; A8D MA.C?8E--

+ -E;.E-

@ -E;.E-

9A-ED :8 E


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+ series

• -ymmetrical airfoil/8ACA &&&B1

•

Asymmetrical airfoil/8ACA '+#'1


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+ -E;.E-

• '+#'

his airfoil has /a1 maximum camber of' occurring at +& chord and /b1

maximum thicness ratio of #'$'4 CAM9E; .8 PE;CE8AE :) C>:;D

+43:CA.:8 :) MA< CAM9E; .8 E8>

:) C>:;D MEA-=;ED );:M 3E#'4 MA< >.C?8E-- .8 PE;CE8AE :)C>:;D


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@ -E;.E-/8ACA '+'1


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@ -E;.E-

• '+' – )irst digit "rst digit when multiplied by

&$#@ gi%es optimum co eFcient of lift

– -econd digit when multiplied by @,gi%es the relati%e position of the point ofmax camber along the chord fromleading edge$

– hird digit whether camber is simple orreGex

– )ourth and "fth digit max thicness of

the airfoil /as a percentage of chord1


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5hy B ,H series

• A turbulent boundary layer results ina higher sin friction drag coeFcientas compared to when the boundary

layer is laminar$ >ence, maintaininga laminar boundary layer o%er alonger portion of the airfoil would

result in a lower drag coeFcient$


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B -E;.E-


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B series eg$BB' I '#@

#st digit JBK indicates that it is a B series airfoil

'nd digit JBK denotes the chordwise position of theminimum pressure in tenths of chord

he suFx J'K indicates that the drag bucetextends L&$' around Clopt $

he digit J'K after the dash indicates that C is &$'$ hus in this case, drag opt bucet extends for C &$& to &$+$ l

he last two digits N#@N indicate that the thicnessratio is #@$


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Cl %s Cd %sCm


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H series

• )urther ad%ancement in maximizingthe laminar Gow achie%ed byseparately identifying the pressure

zones on upper and lower surface


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O series

• -uper critical airfoil

• Delay the wa%e drag

•

Critical mach numberthe freestream mach number atwhich sonic Gow is "rst obtainedsomewhere on the airfoil surface iscalled the critical mach number


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-=PE; C;..CA3 A.;):.3


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Angle of Incidence

The angle between the wing chord line and thefuselage longitudinal axis

Angle of Incidence

The angle between the wing chord line and thefuselage longitudinal axis


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Dihedral

The upward and outward inclination of the wing to the lateralaxis of the airplane

Dihedral

The upward and outward inclination of the wing to the lateralaxis of the airplane


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Wash OutA decrease in the angle of incidence of the wing from root to tip

Wash Out

A decrease in the angle of incidence of the wing from root to tip

Root

Tip


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AnhedralThe downward and outward inclination of the wing to the lateral

axis of the airplane

Anhedral

The downward and outward inclination of the wing to the lateral

axis of the airplane

Wing Span

Wing Span


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Wing TipThe outboard end of the wing where the wing airfoil

shape stops

Wing Tip

The outboard end of the wing where the wing airfoil

shape stops

Wing Span

The distance from wing tip to wing tip

Wing Span

The distance from wing tip to wing tip


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Di6erent plan form of wing


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8ext class

• Aspect ratio


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han u

airfoils and wings

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