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This section includes InterviewSolutions, each offering curated multiple-choice questions to sharpen your knowledge and support exam preparation. Choose a topic below to get started.

51.

The 3D flow characteristic attributed to the wings is a by-product of_____(a) Pressure imbalance over top and bottom surfaces of the wing(b) Pressure imbalance between leading and trailing edge of the airfoil(c) Thickness of the wing(d) Extra lift producedI have been asked this question in class test.I need to ask this question from Downwash and Induced Drag topic in chapter Flow over Airfoils over Finite Wing of Aerodynamics

Answer»

Correct answer is (a) Pressure IMBALANCE over top and bottom surfaces of the WING

Easiest EXPLANATION: Lift over an AIRFOIL is produced by the pressure difference over top and bottom surfaces of airfoil. But for the finite wings, this creates a by-product in the form of span-wise FLOW, which gives a 3D flow. Thickness of the wing and extra lift produced are vague options.

52.

Is change in lift distribution is known as lift section?(a) True(b) FalseThe question was asked in an interview for job.This intriguing question comes from Prandtl’s Classical Lifting-Line Theory topic in chapter Flow over Airfoils over Finite Wing of Aerodynamics

Answer» RIGHT choice is (a) True

The best I can explain: The change in lift distribution is known at given lift section, it is possible to predict how that section influences the lift over its NEIGHBORS, the VERTICAL induced VELOCITY, up wash or down wash can be quantified using the velocity distribution with in VORTEX.
53.

The incorrect difference between airfoil and wings is_______(a) Presence of induced drag in wings(b) Different effective angles of attack seen by(c) Difference in the lift-curve slope(d) Lift slope of the wing is higher than of airfoilThe question was posed to me during an online exam.The above asked question is from Prandtl’s Classical Lifting-Line Theory topic in section Flow over Airfoils over Finite Wing of Aerodynamics

Answer»

Correct choice is (d) Lift slope of the wing is higher than of AIRFOIL

To explain I would say: The finite wing has a lower lift slope than infinite wing (airfoil). This is another difference than the presence of induced drag between wings and airfoil. Also, the effective ANGLES of ATTACK are different for both, being the same only when the lift is zero (at zero lift angle of attack).

54.

The lift coefficient for the airfoil section on a wing ______(a) Depends on local lift slope for airfoil(b) Is same for the entire wing(c) Is equal to the aerodynamic twist(d) Is constant alwaysThis question was addressed to me in a national level competition.I would like to ask this question from Prandtl’s Classical Lifting-Line Theory topic in chapter Flow over Airfoils over Finite Wing of Aerodynamics

Answer»

Right option is (a) Depends on local lift slope for airfoil

Easy explanation: In WINGS, the lift coefficient for local airfoil SECTION is equal to the local airfoil lift curve slope (2π for thin airfoils) into effective angle of ATTACK MINUS zero lift angle of attack. THUS, it may or may not be same for the entire wing and is not equal to the aerodynamic twist.

55.

The lift distribution goes to zero at the tips for the finite wings.(a) False(b) True(c) Only true for elliptical wings(d) Only true for rectangular wingThis question was addressed to me in an interview for job.Asked question is from The Vortex Filament, the Biot-Savart Law, Helmholtz Theorem topic in division Flow over Airfoils over Finite Wing of Aerodynamics

Answer»

Correct option is (B) True

For explanation I would say: For a finite wing, there is PRESSURE equilibrium from the bottom to the TOP of the wing, which makes the lift at the TIPS zero. This is true for all wing SHAPES.

56.

Is lift and drag are the total aerodynamic force acting the body?(a) True(b) FalseThe question was posed to me in semester exam.My doubt is from Downwash and Induced Drag topic in portion Flow over Airfoils over Finite Wing of Aerodynamics

Answer»

The correct option is (a) True

For explanation I WOULD SAY: The total AERODYNAMIC force acting on a body is usually thought of as having two component of force parallel to the ONCOMING flow is called drag and the component perpendicular to the oncoming flow is called LIFT.

57.

Is Newton’s third law of motion is an application for lift on airfoil?(a) False(b) TrueI have been asked this question in an online quiz.The above asked question is from Downwash and Induced Drag topic in division Flow over Airfoils over Finite Wing of Aerodynamics

Answer»

Correct answer is (b) True

For explanation: Lift on airfoil is an example of the application of Newton’s third LAW of motion. The force REQUIRED to CREATE the downwash is equal in magnitude and opposite in direction to the lift force on the airfoil.

58.

For a finite wing, the local relative wind differs by the free-stream velocity by some angle. This angle is called as ____(a) Angle of attack(b) Twist angle(c) Relative angle of attack(d) Induced angle of attackThis question was posed to me in quiz.My question is from Downwash and Induced Drag in chapter Flow over Airfoils over Finite Wing of Aerodynamics

Answer» CORRECT option is (d) Induced angle of attack

The BEST explanation: For a wing, induced velocity in the downward direction is PRESENT apart from the free-stream velocity. The resultant of both (RELATIVE local wind) is inclined to the free-stream velocity by an angle, which is called the induced angle of attack.
59.

The infinite downwash at the wing tips for a single horseshoe vortex in Prandtls lifting line theory was a wrong result. Which of the following does not relate to the correction made?(a) Superimposition of horseshoe vortices(b) Lifting line along the span(c) Trailing vortices only at the tip(d) Different length of bound vorticesThe question was posed to me during an online exam.Query is from Prandtl’s Classical Lifting-Line Theory topic in division Flow over Airfoils over Finite Wing of Aerodynamics

Answer»

Right CHOICE is (c) TRAILING vortices only at the tip

Best explanation: The downwash due to a single horseshoe vortex in Prandtls lifting line theory gave a wrong result as infinite downwash at the WING tips. This was corrected by assuming a superimposition of many horseshoe vortices, each with different length of bound vortices lying along the span on a line, called lifting line. This gave many trailing vortices distributed along the span as WELL.

60.

Is Biot-savart law is used for computing the resultant magnetic field?(a) True(b) FalseI had been asked this question in a job interview.My question is from The Vortex Filament, Biot-Savart Law, Helmholtz Theorem topic in division Flow over Airfoils over Finite Wing of Aerodynamics

Answer»

Right answer is (a) True

Easy explanation: The biot-savart law is USED for computing the resultant magnetic FIELD at POSITION r in 3D –space generated by a steady current. Steady current is a continual flow of charges which does not charge wit time and the charge NEITHER accumulates nor depletes at any point.

61.

Is prandtl lifting line theory is a mathematical model that predicts lift distribution over a three-dimensional wing?(a) True(b) FalseI got this question in an online interview.I'm obligated to ask this question of The Lifting Surface Theory in portion Flow over Airfoils over Finite Wing of Aerodynamics

Answer»

Right CHOICE is (a) True

The explanation is: The prandtl lifting LINE theory is a mathematical models that PREDICTS LIFT DISTRIBUTION over a three dimensional wing based on its geometry. It is also known as the lanchester-prandtl wing theory. It was used to calculate lift on the wing.

62.

A condition in which the wing has different values of α along the span is called as ______(a) Washout(b) Geometric twist(c) Aerodynamic twist(d) WashinThe question was posed to me at a job interview.This is a very interesting question from The Vortex Filament, the Biot-Savart Law, Helmholtz Theorem topic in portion Flow over Airfoils over Finite Wing of Aerodynamics

Answer»

Correct option is (b) Geometric TWIST

The best I can explain: Some wings are TWISTED i.e. they have different geometric ANGLE of attack at different places along the span-called geometric twist. The other terms do not MEAN the same.

63.

Select the incorrect statement regarding the terminology used in the study of incompressible flow over finite wings.(a) Induced drag is finite(b) Circulation is constant(c) Downwash is absent(d) Vorticity induces velocityThis question was addressed to me in quiz.This is a very interesting question from The Vortex Filament, the Biot-Savart Law, Helmholtz Theorem topic in division Flow over Airfoils over Finite Wing of Aerodynamics

Answer»

Right option is (c) Downwash is absent

Explanation: Due to the presence of downwash, lift is no more VERTICAL. The induced drag is caused by the non-vertical component of lift. Circulation is constant, as the KELVIN’s circulation statement states. The VORTEX filament induces velocity, which DEPENDS on the STRENGTH of vortex (constant circulation).

64.

Is induced drag produce lift?(a) True(b) FalseThe question was posed to me during an interview for a job.Question is taken from Downwash and Induced Drag in section Flow over Airfoils over Finite Wing of Aerodynamics

Answer»

The correct CHOICE is (a) True

The BEST explanation: In aerodynamics induced drag will produce lift. It is an aerodynamic drag force that occurs WHENEVER a moving object redirects the airflow coming at it. This drag force occurs in airplanes due to wings or a LIFTING body redirecting air to cause lift.

65.

According to the reasoning given by Prandtl for his lifting line theory, finite wing is like a ________(a) Bound vortex(b) Horseshoe vortex(c) Free vortex(d) Trailing vortexThis question was posed to me in an interview.I want to ask this question from Prandtl’s Classical Lifting-Line Theory in portion Flow over Airfoils over Finite Wing of Aerodynamics

Answer»

Right answer is (a) Bound VORTEX

Explanation: PRANDTL reasoned that the finite wing can be thought LIKE a bound vortex, which is opposite to the free vortex. SINCE a vortex filament cannot end in the fluid, it is ASSUMED that there are two trailing vortices which gives the appearance like that of a horseshoe vortex.

66.

The total drag coefficient for a wing is given by______(a) cd=\(\frac {D_f+D_P+D_i}{Sq_∞}\)(b) Cd=\(\frac {D_f+D_P}{Sq_∞}\)(c) Cd=\(\frac {D_f+D_P+D_i}{Sq_∞}\)(d) Cd=\(\frac {D_f+D_P}{Sq_∞}\)+DiThe question was posed to me in an interview for internship.My question comes from Downwash and Induced Drag in division Flow over Airfoils over Finite Wing of Aerodynamics

Answer»

Right choice is (c) Cd=\(\FRAC {D_f+D_P+D_i}{Sq_∞}\)

To explain: For wing, the TOTAL drag comprises of viscous drag plus the INDUCED drag. The COEFFICIENT of total drag is given by Cd=\(\frac {D_f+D_P+D_i}{Sq_∞}\), which is NOTHING but Cd=\(\frac {D_f+D_P}{Sq_∞}+\frac {D_i}{Sq_∞}\)i.e. Cd=cd+Cdi.

67.

Which is the wrong implication of the elliptical lift distribution for a wing?(a) Circulation varies elliptically along span(b) Span length does not affect circulation(c) Lift is zero at the tips(d) Maximum lift is at the centerThe question was posed to me during an interview.This is a very interesting question from Prandtl’s Classical Lifting-Line Theory in portion Flow over Airfoils over Finite Wing of Aerodynamics

Answer»

The correct option is (b) Span length does not affect circulation

Best EXPLANATION: The elliptical lift distribution comes from the elliptical distribution of circulation ALONG the span. The lift (or circulation) involves span length in the governing equations and hence the wrong statement. Lift is ZERO at the WING tips and maximum at the CENTER.

68.

Is integral is usually around a closed curve?(a) True(b) FalseThe question was posed to me during an interview.My doubt stems from The Vortex Filament, Biot-Savart Law, Helmholtz Theorem topic in section Flow over Airfoils over Finite Wing of Aerodynamics

Answer» CORRECT answer is (a) True

The EXPLANATION is: The integral is usually around a closed curve since stationary electric currents can only flow around closed paths when they are bounded. However, the law ALSO applies to infinitely long wires as used in the definition of the SI UNIT of electric current.
69.

Which is the incorrect analogyout of the following regarding Biot-Savart law?(a) Induced velocity: Magnetic induction(b) Vortex Filament: Current-carrying Wire(c) Vorticity: Velocity(d) Aerodynamics: ElectromagnetismThis question was posed to me by my college director while I was bunking the class.My question comes from The Vortex Filament, the Biot-Savart Law, Helmholtz Theorem topic in section Flow over Airfoils over Finite Wing of Aerodynamics

Answer»

Right answer is (C) Vorticity: Velocity

Easy explanation: The Biot-Savart law holds an analogy in aerodynamics and electromagnetism. The induced air CURRENT (induced fluid velocity) for a vortex filament can be thought ANALOGOUS to the induced magnetic field (magnetic induction) for a current-carrying wire. The CIRCULATION can be thought of as magnetic flux and vorticity is like the current.

70.

The angle between the chord line and the direction of free-stream velocity is called the angle of attack.(a) True for airfoil only(b) True for wing only(c) True for airfoil and partially true for wings(d) FalseThis question was addressed to me during an interview.This key question is from Downwash and Induced Drag in section Flow over Airfoils over Finite Wing of Aerodynamics

Answer»

Right CHOICE is (c) True for airfoil and partially true for wings

Easiest explanation: For an airfoil, the ANGLE between the chord LINE and the direction of free-stream velocity is called the angle of attack. For the wings, the precise name is geometric angle of attack. Hence the given STATEMENT is only partially true for a wing.

71.

The circulation at the center for an elliptical wing distribution does not depend upon ________(a) Lift distribution(b) Density of fluid at center(c) Free-stream velocity(d) Total span lengthThis question was posed to me during an online interview.This is a very interesting question from Prandtl’s Classical Lifting-Line Theory topic in chapter Flow over Airfoils over Finite Wing of Aerodynamics

Answer»

The correct answer is (b) Density of FLUID at center

For EXPLANATION: The circulation at the center for an elliptical WING distribution is dependent directly on the total LIFT which can be found from the lift distribution. ALSO, it depends upon the free-stream velocity, total span length and free-stream fluid density.

72.

Is wing tips vortices produce the down wash?(a) True(b) FalseI have been asked this question during an interview.The doubt is from Downwash and Induced Drag in portion Flow over Airfoils over Finite Wing of Aerodynamics

Answer»

Right option is (a) True

Explanation: The wing tip VORTICES PRODUCE a downwash of AIR behind the wing which is very STRONG near the wing tips and DECREASE toward the wing root. The effective angle of attack of the wing is decreased by the downwash.

73.

Is it difficult to predict the amount of lift that a wing geometry will generate?(a) False(b) TrueI had been asked this question in an online quiz.My question is from Prandtl’s Classical Lifting-Line Theory topic in portion Flow over Airfoils over Finite Wing of Aerodynamics

Answer»

Correct answer is (b) True

Explanation: It is difficult to PREDICT analytically the overall amount of lift that a wing of GIVEN geometry will generate. The lifting line theory yields the lift distribution along the span-wise DIRECTION, based only on the wing geometry and flow conditions.

74.

The velocity induced by an infinite vortex filament, with strength Γ at some point is correctly given as______ (r, h are the distance and height to the point respectively).(a) V=\(\frac {\Gamma }{2\pi h}\)(b) V=\(\frac {\Gamma }{2\pi r}\)(c) V=\(\frac {\Gamma }{2h}\)(d) V=\(\frac {\Gamma }{2r}\)I had been asked this question in quiz.My question is from The Vortex Filament, the Biot-Savart Law, Helmholtz Theorem topic in division Flow over Airfoils over Finite Wing of Aerodynamics

Answer»

Right answer is (a) V=\(\frac {\Gamma }{2\pi h}\)

For explanation: The velocity induced at a POINT at a distance r (PERPENDICULAR distance h) from an INFINITE, straight vortex filament is calculated using Biot-Savart law. This is same as the velocity for a point vortex, which is V=\(\frac {\Gamma }{2\pi h}\) where Γ is the strength of the vortex filament.

75.

The incorrect statement regarding Helmholtz theorems is____(a) Valid for all inviscid flows(b) Γ remains constant along vortex filament(c) Describes vortex behavior(d) Vortex filament forms a closed loop or extends till the boundaries of the fluidThe question was posed to me in an internship interview.My question is based upon The Vortex Filament, the Biot-Savart Law, Helmholtz Theorem topic in section Flow over Airfoils over Finite Wing of Aerodynamics

Answer»

Correct option is (a) Valid for all inviscid FLOWS

To explain I would say: The Helmholtz THEOREMS are valid for inviscid, incompressible flows and describe the vortex behavior. ACCORDING to these theorems, the strength of vortex filament is constant along its length and a vortex filament cannot end in a fluid. According to the latter one, the filament must form a CLOSED loop or extend TILL the boundaries of the fluid.

76.

The downward velocity induced by the trailing vortex in the vicinity of the wing-tips is called as _____(a) Downwash(b) Local relative velocity(c) Effective velocity(d) Wing velocityThis question was posed to me in examination.My question is from Downwash and Induced Drag in division Flow over Airfoils over Finite Wing of Aerodynamics

Answer»

Right choice is (a) Downwash

The best explanation: The trailing vortices, in the VICINITY of the wing-tips, drag along with them the surrounding air. This INDUCES a SMALL velocity COMPONENT in the downward direction. This is called downwash. NONE of the other terms describe this induced velocity.

77.

Select the incorrect statement for a flow over wings.(a) Induced drag comes from pressure- drag(b) Pressure imbalance makes D’Alembert’s paradox does not occur(c) 3D flow over wings cause induced drag(d) Induced drag is a ‘type’ of pressure- dragI got this question in an interview for job.My query is from Downwash and Induced Drag topic in division Flow over Airfoils over Finite Wing of Aerodynamics

Answer»

The correct OPTION is (a) Induced drag COMES from pressure- drag

Explanation: For a wing, 3D FLOW causes a pressure imbalance in the direction of FREE – stream velocity, which is the drag. Thus, induced drag is a type of pressure-drag. But it is not caused by pressure drag.

78.

The trailing vortex is formed at each wing-tip as there is a circulatory motion established by the____(a) Leaking flow at the wing- tips(b) Flowing wind(c) Viscosity(d) Air tornadoesThis question was addressed to me by my college director while I was bunking the class.I want to ask this question from Downwash and Induced Drag in section Flow over Airfoils over Finite Wing of Aerodynamics

Answer»

The correct answer is (a) Leaking flow at the WING- tips

The explanation is: The flow has a TENDENCY to ‘leak’ around the wing-tips. This flow makes a circulatory motion that trails DOWNSTREAM of the finite weak, GIVING rise to trailing vortices. This flow is POSSIBLE because of viscosity but it doesn’t happen because of viscosity.

79.

The span-wise component of flow over the top surface of the wing flows______(a) From wing-tip to root(b) From root to wing-tip(c) Along the free-stream direction(d) Perpendicular to the wing upwardsThe question was posed to me in unit test.My question is taken from Downwash and Induced Drag topic in division Flow over Airfoils over Finite Wing of Aerodynamics

Answer»

The correct OPTION is (a) From wing-tip to root

Best explanation: The pressure imbalance is such that there is a low pressure region on TOP and HIGH pressure region at the BOTTOM. This creates a flow from the bottom surface towards the top surface of the wing. Naturally, the flow moves from the wing-tips towards the wing root.

80.

Is local induced change the angle of attack on a given section of a wing?(a) True(b) FalseThe question was posed to me in examination.Question is from Prandtl’s Classical Lifting-Line Theory in portion Flow over Airfoils over Finite Wing of Aerodynamics

Answer»

Correct option is (a) True

For EXPLANATION I would say: The LOCAL induced change of angle of attack on a given section can be quantified with the integral sum of the DOWNWASH induced by every other wing section. In TURN, the integral sum of the lift on each down washed wing section is equal to the total desired amount of lift.

81.

Is shed vortex can be modeled at vertical velocity?(a) True(b) FalseThe question was posed to me at a job interview.My doubt stems from Prandtl’s Classical Lifting-Line Theory topic in chapter Flow over Airfoils over Finite Wing of Aerodynamics

Answer»

Right choice is (a) True

Easy explanation: The shed vortex can be MODELED as a vertical velocity distribution. The up wash and downwash INDUCED by the shed vortex can be computed at each neighbor segment. This sideways influence up wash on the outboard, downwash on the in a BOARD.

82.

Is vortex filament cannot begin or terminate in the air?(a) True(b) FalseI have been asked this question in my homework.This intriguing question originated from Prandtl’s Classical Lifting-Line Theory in section Flow over Airfoils over Finite Wing of Aerodynamics

Answer»

Correct option is (a) True

Explanation: The vortex filament cannot BEGIN or TERMINATE in the air, as such, any span wise change in lift can be modeled as the shedding of a vortex filament down the flow, BEHIND the wing. This shed vortex, hose strength is the derivative of the LOCAL wing.

83.

In Biot-Savart law, the circulation taken about any path enclosing the vortex filament is____(a) Constant(b) Depends on the local strength(c) Zero(d) Path-dependentThis question was addressed to me in an online interview.My question comes from The Vortex Filament, the Biot-Savart Law, Helmholtz Theorem topic in chapter Flow over Airfoils over Finite Wing of Aerodynamics

Answer»

The correct choice is (a) CONSTANT

To explain I WOULD say: The circulation taken about any path enclosing the vortex FILAMENT is a constant. This is true for a straight as well as CURVED filament. (Kelvin’s circulation THEOREM).

84.

Which of the following is incorrect for a finite wing?(a) Streamlines on the top surface bend towards the root(b) Span-wise flow at the bottom surface is towards the tip(c) Higher pressure region exists at the top surface(d) Streamlines on the bottom surface bend towards the tipI got this question by my college professor while I was bunking the class.This key question is from Downwash and Induced Drag topic in portion Flow over Airfoils over Finite Wing of Aerodynamics

Answer»

Correct choice is (C) Higher pressure region exists at the top surface

For EXPLANATION: There is higher pressure region at the bottom and lower pressure at the top. Due to which the flow moves from the wing root at the bottom TOWARDS the wing-tips, turns UPWARDS and moves towards the wing root at the top surface. Thus, streamlines on the bottom surface BEND towards the tip and vice versa happens at the top surface.

85.

Tapered wings are used more rather than elliptical wing planforms practically. The reason being______(a) Easy to manufacture than elliptic wings(b) Aspect ratio more important for low induced drag(c) Tapered wing resembles elliptic wing highly(d) Tapered wing is another name for elliptic wingI had been asked this question in exam.The query is from Prandtl’s Classical Lifting-Line Theory topic in division Flow over Airfoils over Finite Wing of Aerodynamics

Answer»

Correct choice is (a) Easy to manufacture than ELLIPTIC WINGS

Best EXPLANATION: In reality, tapered wings are preferred over elliptic wings because they are easier to manufacture (they have straight edges). But the resemblance to elliptic wings (variation of δ) is secondary to reduce wing induced drag compared to the aspect ratio. Here we are only asked why tapered wings used; the ANSWER is easy to manufacture.

86.

Is 2D version of Biot-Savart equation is used, when the sources are invariant in one direction?(a) True(b) FalseI had been asked this question in an internship interview.This intriguing question originated from The Vortex Filament, Biot-Savart Law, Helmholtz Theorem in portion Flow over Airfoils over Finite Wing of Aerodynamics

Answer»

Right ANSWER is (a) True

Easiest explanation: The 2D version of the biot-savart equation is used when the sources are invariant in ONE direction.in general the current NEED not flow only in a plane normal to the invariant direction and it is GIVEN by the FORMULATIONS given above work well when the current can be approximated as running through an infinitely-narrow wire.

87.

Is circular filament is of constant thickness?(a) True(b) FalseThe question was asked in final exam.The origin of the question is The Vortex Filament, Biot-Savart Law, Helmholtz Theorem in portion Flow over Airfoils over Finite Wing of Aerodynamics

Answer»

Right choice is (a) True

The BEST explanation: The closed filaments, a circular filament of CONSTANT THICKNESS and vorticity is in self equilibrium, this is easily verified using z=e, consider STRAIGHT filaments placed on the z-axis with constant vorticity along the curve.

88.

Is vortex filament is a very thin strip?(a) True(b) FalseThe question was posed to me in class test.Origin of the question is The Vortex Filament, Biot-Savart Law, Helmholtz Theorem in section Flow over Airfoils over Finite Wing of Aerodynamics

Answer»

Right ANSWER is (a) True

To explain: A VORTEX filament is a very thin strip of VORTICITY in x-y plane. The small thickness assumption will be USED to characterize the filament by its center line curve. Mass conservation and material transport of vorticity are used to describe variation in local thickness and vorticity.

89.

Biot-Savart law can be used to describe inviscid, incompressible flows.(a) True(b) FalseI have been asked this question during an online interview.This interesting question is from The Vortex Filament, the Biot-Savart Law, Helmholtz Theorem in portion Flow over Airfoils over Finite Wing of Aerodynamics

Answer»

Right option is (a) TRUE

To explain I would say: Biot-Savart law is a CONSEQUENCE of potential theory and potential theory provides description for electromagnetic FIELDS and inviscid, incompressible flows as WELL. Thus, it is true.

90.

Is air pressure on the top of the wing is lower than the pressure below the wing?(a) True(b) FalseI had been asked this question in semester exam.The doubt is from Downwash and Induced Drag in section Flow over Airfoils over Finite Wing of Aerodynamics

Answer»

The CORRECT answer is (a) True

For EXPLANATION: For a lifting wing, the air pressure on the top of the wing is lower than the pressure below the wing. The TIP of the wing, the air is free to move from the region of high pressure into the region of low pressure. The resulting flow at the left by the two CIRCULAR blue lines with the ARROWHEADS of flow direction.

91.

For an inviscid, incompressible flow over finite wings, D’Alembert’s paradox occurs.(a) True(b) FalseI got this question by my college professor while I was bunking the class.This interesting question is from Downwash and Induced Drag in chapter Flow over Airfoils over Finite Wing of Aerodynamics

Answer»

Right ANSWER is (B) False

Explanation: The induced drag is caused by a component of lift which is not vertical. Therefore, even in the absence of skin-friction or FLOW separation, drag is not zero. For a wing, D’Alembert’s paradox does not OCCUR.

92.

Is down wash is change in direction of lift?(a) True(b) FalseThis question was posed to me during an interview.This intriguing question comes from Downwash and Induced Drag in section Flow over Airfoils over Finite Wing of Aerodynamics

Answer»

The correct ANSWER is (a) True

Best explanation: Down wash is the change in DIRECTION of air deflected by the aerodynamic action of an airfoil, wing, or helicopter rotor blade in motion, as part of the PROCESS of producing lift. When the RELATIVE wind moves from nose to down side of the wing which causes change in direction of air and PRODUCE lift.

93.

Induced drag is generated by a component of lift for a finite wing.(a) True(b) FalseThe question was asked by my college director while I was bunking the class.This interesting question is from Downwash and Induced Drag topic in portion Flow over Airfoils over Finite Wing of Aerodynamics

Answer»

The correct answer is (a) True

Explanation: The local LIFT vector is not aligned perpendicular to the free-stream velocity vector for a wing. Lift is perpendicular to local relative wind. This CAUSES a component of local lift in the direction of drag, CALLED induced drag.

94.

The airfoil and the wing behave exactly the same way in terms of aerodynamic properties.(a) True(b) FalseI have been asked this question in final exam.I'd like to ask this question from Downwash and Induced Drag in division Flow over Airfoils over Finite Wing of Aerodynamics

Answer»

The correct CHOICE is (b) False

To elaborate: The airfoil can be thought of as an INFINITE wing. It is indeed a section of a wing. While on the other hand, wing means a finite wing, until SPECIFIED otherwise. CLEARLY, the PROPERTIES are different for a wing and an airfoil.