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The discussion
so far has not taken the finite wingspan of the aircraft into account.
The photograph and diagram show the consequence of the finite wing. The
bound vortex that has just been discussed leaves the starting vortex at the
takeoff point. At the wing tips, the pressure distribution that was responsible
for the starting vortex creates a wing tip vortex and the closed vortex loop
illustrated in the diagram results. The two tip vortices rotate in the opposite
sense and total angular momentum is again conserved.
The photograph
shows the vortex trail behind a crop-dusting plane made visible by the
dust injected into the flow field. Similar trails can be seen behind aircraft
at high altitude where the tip vortex nucleates water vapor condensation
(contrails). |
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