Airfoils and wings - Aerodynamics - Aerospace Engineering Previous Year Questions

1

2007 · Aerospace Engineering · Aerodynamics · Airfoils and wings

Aerospace Engineering (AE) 2007

The Joukowskii airfoil is studied in aerodynamics because

A

it is used in many aircraft

B

it is easily transformed into a circle, mathematically

C

it has a simple geometry

D

it has the highest lift curve slope among all airfoils

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2

2007 · Aerospace Engineering · Aerodynamics · Airfoils and wings

Aerospace Engineering (AE) 2007

Two airfoils of the same family are operating at the same angle of attack. The dimensions of one airfoil are twice as large as the other one. The ratio of the minimum pressure coefficient of the larger airfoil to the minimum pressure coefficient of the smaller airfoil is

A

4.0

B

2.0

C

1.0

D

0.5

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3

2007 · Aerospace Engineering · Aerodynamics · Airfoils and wings

Aerospace Engineering (AE) 2007

Wing A has a constant chord c and span b. Wing B is identical but has a span 4b. When both wings are operating at the same geometric angle of attack at subsonic speed, then:

A

wings A and B produce the same lift coefficient

B

wing A produces a smaller lift coefficient than wing B

C

wing A produces a greater lift coefficient than wing B

D

the freestream Mach number decides which wing produces the greater lift coefficient

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4

2007 · Aerospace Engineering · Aerodynamics · Airfoils and wings

Aerospace Engineering (AE) 2007

A turbulent boundary layer remains attached over a longer distance on the upper surface of an airfoil than does a laminar boundary layer, because

A

the turbulent boundary layer is more energetic and hence can overcome the adverse pressure gradient better

B

the laminar boundary layer develops more skin friction and hence slows down more rapidly

C

turbulence causes the effective coefficient of viscosity to reduce, resulting in less loss of momentum in the boundary layer

D

the turbulent boundary layer is thicker, hence the velocity gradients in it are smaller, therefore viscous losses are less

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5

2007 · Aerospace Engineering · Aerodynamics · Airfoils and wings

Aerospace Engineering (AE) 2007

An airfoil section is known to generate lift when placed in a uniform stream of speed \( U_\infty \) at an incidence \( \alpha \). A biplane consisting of two such sections of identical chord \( c \), separated by a distance h is shown in the following figure: With regard to this biplane, which of the following statements is true?

A

Both the airfoils experience an upwash and an increased approach velocity

B

Both the airfoils experience a downwash and a decreased approach velocity

C

Both the airfoils experience an upwash and airfoil A experiences a decreased approach velocity while airfoil B experiences an increased approach velocity

D

The incidence for the individual sections of the biplane is not altered

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6

2007 · Aerospace Engineering · Aerodynamics · Airfoils and wings

Aerospace Engineering (AE) 2007

The span-wise lift distribution for three wings is shown in the following figure:
In the above figure, \( c_l \) refers to the section lift coefficient, \( C_L \) refers to the lift coefficient of the wing, \( y \) is the coordinate along the span and \( s \) is the span of the wing. A designer prefers to use a wing for which the stall begins at the root. Which of the wings will he choose?

A

P

B

Q

C

R

D

None

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7

2007 · Aerospace Engineering · Aerodynamics · Airfoils and wings

Aerospace Engineering (AE) 2007

The lift curve slope of this wing is

A

0.10 per deg

B

0.092 per deg

C

0.075 per deg

D

0.050 per deg

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8

2008 · Aerospace Engineering · Aerodynamics · Airfoils and wings

Aerospace Engineering (AE) 2008

The maximum thickness to chord ratio for the NACA 24012 airfoil is

A

0.01

B

0.12

C

0.24

D

0.40

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9

2008 · Aerospace Engineering · Aerodynamics · Airfoils and wings

Aerospace Engineering (AE) 2008

Laminar flow airfoils are used to reduce

A

trim drag

B

skin friction drag

C

induced drag

D

wave drag

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10

2008 · Aerospace Engineering · Aerodynamics · Airfoils and wings

Aerospace Engineering (AE) 2008

Consider a symmetric airfoil at an angle of attack of 4 degrees. Using thin airfoil theory, the magnitude of the moment coefficient about the leading edge is

A

\(2\pi\)

B

\(\pi\)

C

\(\pi^2/60\)

D

\(\pi^2/90\)

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11

2008 · Aerospace Engineering · Aerodynamics · Airfoils and wings

Aerospace Engineering (AE) 2008

The variation of downwash along the span of an untwisted wing of elliptic planform is

A

sinusoidal

B

parabolic

C

elliptic

D

constant

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12

2008 · Aerospace Engineering · Aerodynamics · Airfoils and wings

Aerospace Engineering (AE) 2008

Flow past an airfoil is to be modeled using a vortex sheet. The strength of the vortex sheet at the trailing edge will be

A

0

B

1

C

\(2\pi\)

D

\(\infty\)

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13

2008 · Aerospace Engineering · Aerodynamics · Airfoils and wings

Aerospace Engineering (AE) 2008

The geometrical features of a supercritical airfoil are

A

rounded leading edge, flat upper surface and high camber at the rear

B

sharp leading edge, curved upper surface and high camber at the rear

C

rounded leading edge, curved upper surface and no camber at the rear

D

sharp leading edge, flat upper surface and no camber at the rear

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14

2008 · Aerospace Engineering · Aerodynamics · Airfoils and wings

Aerospace Engineering (AE) 2008

Which one of the following high lift device results in higher stalling angle?

A

split flap

B

Fowler flap

C

plain flap

D

leading edge flap

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15

2008 · Aerospace Engineering · Aerodynamics · Airfoils and wings

Aerospace Engineering (AE) 2008

The wing lift coefficient \(C_L\) is

A

0.66

B

0.51

C

0.44

D

0.34

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16

2008 · Aerospace Engineering · Aerodynamics · Airfoils and wings

Aerospace Engineering (AE) 2008

The induced drag coefficient of the wing \(C_{Di}\) is

A

0.0053

B

0.0087

C

0.0118

D

0.0197

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17

2009 · Aerospace Engineering · Aerodynamics · Airfoils and wings

Aerospace Engineering (AE) 2009

A trailing edge plain flap deflected downward increases the lift coefficient of an airfoil by

A

Increasing the effective camber of the airfoil.

B

Delaying the separation of the flow from the airfoil surface.

C

Increasing the local airspeed near the trailing edge.

D

Controlling the growth of the boundary layer thickness along the airfoil surface.

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18

2009 · Aerospace Engineering · Aerodynamics · Airfoils and wings

Aerospace Engineering (AE) 2009

Thin airfoil theory predicts that the lift slope is \(\frac{dC_l}{d\alpha} = 2\pi\) for

A

Symmetric airfoils only.

B

Cambered airfoils only.

C

Any airfoil shape.

D

Joukowski airfoils only.

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19

2009 · Aerospace Engineering · Aerodynamics · Airfoils and wings

Aerospace Engineering (AE) 2009

A model airfoil in a wind tunnel that is operating at 50 m/s develops a minimum pressure co-efficient of – 6.29 at some point on its upper surface. The local airspeed at that point is

A

50 m/s

B

125 m/s

C

135 m/s

D

150 m/s

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20

2009 · Aerospace Engineering · Aerodynamics · Airfoils and wings

Aerospace Engineering (AE) 2009

A symmetrical airfoil section produces a lift coefficient of 0.53 at an angle of attack of 5 degrees measured from its chord line. An untwisted wing of elliptical planform and aspect ratio 6 is made of this airfoil. At an angle of attack of 5 degrees relative to its chordal plane, this wing would produce a lift coefficient of

A

0.53

B

0.48

C

0.40

D

0.36

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