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 increases as the angle of attack decreases.
II. The strength of wing tip vortices decreases as the aspect ratio decreases.
Wing tip vortices increase if we increase induced drag.This can be caused by for example increased speed, density or lift coefficient.
If we decrease Angle of Attack, lift will be decreased, also decreasing the strength of wing tip vortices.
This shows that statement I is incorrect.
Another factor increasing wing tip vortices is the aspect ratio (λ) of the wing.This is the ratio of the wing span to its mean chord.
The aspect ratio of the wing is equal to the square od the wingspan divided by the wing surface area.
Therefore a short but wide wing has a low aspect ratio but a long, narrow wing has a high aspect ratio.
With a lower aspect ratio, the induced drag is higher, thus increasing wing tip vortices.
With a high aspect ratio, the induced drag is lower, reducing wing tip vortices.
We can therefore state that the relationship between wing tip vortices and aspect ratio is inversely proportional.
Statement number II is incorrect, as the correct answer would be “The strength of wing tip vortices increases as the aspect ratio decreases.
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