What causes the vortex on the tip of this vertical stabilizer (CFD Simulation) This is a computational fluid dynamics simulation of an airfoil that is oriented to look like a vertical stabilizer. After watching the video, it becomes clear that the tip of the stabilizer causes a counter-clockwise vortex (if looking at the trailing edge). According to this answer, vortices only form on vertical stabilizers if a control surface (the rudder) is deflected. In this simulation, the rudder appears to be completely in-line with the rest of the airfoil.

Furthermore, there also appears to be a slight clockwise rotation on the bottom of the stabilizer, where it would attach to the aircraft's tail. This seems even harder to explain, given the opposite rotation and angular velocity of the top one. I can only assume this is partially caused by the disturbances from what look like hinges farther up. Is this reasonable?

TL;DR: What causes the strong vortex on the tip of this vertical stabilizer?
The subtitle of the video states:


  This video shows a high-fidelity CFD simulation of flow control applied to realistic wing profiles using PHASTA and ParaView Catalyst. Work done by Michel Rasquin from Argonne and Ken Jansen from UC Boulder.


Realistic wing profiles sounds like: we're actually looking at a wing in a vertical orientation - or in a horizontal orientation from a viewpoint that causes some confusion. Looking at a wing at some Angle of Attack that creates lift, and therefore the visualised flow pattern. And then the two vortices are caused by the end effect of finite wing span.