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# MCQs on Prandtl’s Classical Lifting-Line Theory – 3

1 - Question

Is prandtl lifting line theory predicts lift distribution over a three dimensional wing?

a) True

b) False

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aExplanation: The prandtl lifting-line theory is a mathematical model that predicts lift distribution over a three dimensional wing based on its geometry. It is also known as the lanchester-prandtl wing theory. The theory was expressed independently by Frederick w. lanchester in 1907.

2 - Question

Is lift over each wing segment is correspond?

a) False

b) True

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aExplanation: On a three-dimensional, finite wing, lift over each wing segment does not correspond simply to what two dimensional analysis predicts. Instead, this local amount of lift is strongly affected by the lift generated at neighboring wing section.

3 - Question

Is it difficult to predict the amount of lift that a wing geometry will generate?

a) False

b) True

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bExplanation: 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.

4 - Question

Is lifting line theory applies to circulation?

a) True

b) False

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aExplanation: The lifting line theory applies the concept of circulation and the kutta-joukowski theorem so that instead of the lift distribution function, the unknown effectively becomes the distribution of circulation over the span.

5 - Question

Is lift distribution over a wing can be modeled with the concept of circulation?

a) True

b) False

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aExplanation: The lift distribution over a wing can be modeled with the concept of circulation. A vortex is shed downstream for every span wise change in lift. Modeling the local lift with local circulation allows us to account for the influence of one section over its neighbors.

6 - Question

Is vortex filament cannot begin or terminate in the air?

a) True

b) False

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aExplanation: 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.

7 - Question

Is shed vortex can be modeled at vertical velocity?

a) True

b) False

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aExplanation: 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.

8 - Question

Is change in lift distribution is known as lift section?

a) True

b) False

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aExplanation: 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.

9 - Question

Is local induced change the angle of attack on a given section of a wing?

a) True

b) False

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aExplanation: 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.

10 - Question

Is additional term can be added to make an aircraft wing station?

a) True

b) False

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aExplanation: When the aircraft is rolling, an additional term can be added that adds the wing station distance multiplied by the rate of roll to give an additional angle of attack change, which introduces non-zero even coefficient in the equation that must be an accounted for it.