The wingtip vortex arises primarily from what mechanism?

• A. Pressure differences between upper and lower surfaces create a rotating flow
• B. Friction with the air at the surface
• C. Wind shear
• D. Thermal convection

Answer: (A)

Pressure difference between the wing's upper and lower surfaces creates a rotating flow around the wingtips, forming the wingtip vortex. Lift generates high pressure beneath the wing and lower pressure on top, so air moves around the tip from the bottom to the top to try to equalize those pressures. That motion wraps into a spiral behind the wing, producing the characteristic vortex. Friction with the surface is a boundary-layer effect and isn’t the primary cause of the vortex, wind shear can alter the vortex after it forms, and thermal convection isn’t involved in its creation.