Is there error in this vorticity plot
 

Hi,

I'm trying to simulate an naca0012 airfoil oscillating in a flowfield. Re~10,000

I've got this vorticity plot

http://usera.imagecave.com/quarkz/temp_vorticity.jpg

Unlike other vorticity plots, which have orderly vortices being shed, this one doesn't seem "normal". Is there something wrong with my code?

Or how do I anaylze vorticity plots like this? Is there any book which have a good discussion on these?

Thanks alot!