The <a href="https://en.wikipedia.org/wiki/vortex" class="extiw" title="en:vortex">vortex</a> shed due to the span-wise change in lift on a wing can be represented as a velocity distribution perpendicular to the direction of flight.
<p>The vortex causes upwash outboard, and downwash inboard of the considered element.
</p>
<i>Part of a series of illustrations meant to illustrate the <a href="https://en.wikipedia.org/wiki/lifting-line_theory" class="extiw" title="en:lifting-line theory">lifting-line theory</a>.</i>
<a href="//commons.wikimedia.org/wiki/User:Ariadacapo" title="User:Ariadacapo">Olivier Cleynen</a>
<span class="int-own-work" lang="en">Own work</span>