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Which of these statements about the strength of wing tip vortices are correct or incorrect?

I. Assuming no flow separation, the strength of wing tip vortices decreases as the angle of attack increases.
II. The strength of wing tip vortices is not affected by aspect ratio.

  • A
    I is correct, II is correct.
  • B
    I is incorrect, II is incorrect.
  • C
    I is correct, II is incorrect.
  • D
    I is incorrect, II is correct.

Wing tip vortices are a by-product of lift. They are caused by the pressure differential between the top and bottom of the wing, which causes an updraft of high pressure air around the tip of the wing. This updraft turn into a downdraft behind the wing, creating a vortex. The higher the pressure difference between the top and bottom of the wing, the stronger the vortices.

This question is specifically asking for:

  • Angle of attack: The strength of the vortices (and therefore also induced drag) is proportional to the angle of attack. Therefore; the strength of the vortices increase as the angle of attack increases. And also; the strength of the vortices decrease as the angle of attack decreases. Therefore statement 1 is incorrect!

  • Aspect ratio: The strength of the vortices is inversely proportional with the aspect ratio. Meaning that the strength of the wing tip vortices increase as the aspect ratio decreases. And vice versa: the strength decreases as the aspect ratio increases. Therefore statement 2 is incorrect!

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  • Poland
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