Does this vorticity plot make sense?

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I'm trying to plot the vorticity field for lid-driven cavity flow. Because I'm looking at 2D flow, the vorticity is plotted as a scalar field The flow field is clockwise, and I would expect the majority of the resulting vorticity field to be negative (right hand rule). However, it seems as thought it has some weird behavior. What do you think?

http://i.imagebanana.com/img/h3ke22hx/Selection_049.png

 

[RandomGuy88]

Having never studied or even read anything about this flow, I would say it looks reasonable. What do you think is weird about it?

 

[mfb]

If the outer parts do not rotate quicker than the inner parts, you don't need a negative vorticity in the whole plane. The upper edge is a bit surprising with its large negative vorticity.

 

[RandomGuy88]

The large negative vorticity at the upper part is exactly what I would have expected since it is a free shear layer. Of course I don't know what the magnitude should be, and we don't know what the units are.

What are the units? Also, what is the free stream velocity?

As the flow turns down near the far right edge, positive vorticity is generated along the wall due to the boundary layer that forms on that surface. Positive vorticity would form along the walls regardless of how quickly the outer and inner parts are rotating (as long as they are rotating and generating a flow along the walls). If the flow were rotating faster I would expect the layer of positive vorticity to become thinner and for its magnitude to increase.