Determine the centre of vortex
 

The plot shown is direct numerical solution of the Ahmed body.
My aim is to determine the centre of vortex using Fortran by reading the solution P,u,v (pressure and velocity).
So far I have used minimum(for top vortex) or maximum(for bottom vortex) vortex value to determine the centre of vortex.
But in the present case I have to specify initially the approximate position..which then finds minimum or maximum vorticity value around that window.
Now, I do not want to give the initial approximate position of vortex.
Is there a way (mathematically) to determine the centre without giving approximate position?
like curl(u)/grad(u) ? I am not sure..
Let me know if I am not clear in stating above problem.
Thanks in advance

Try searching for maximums of vorticity (curl of velocity) magnitudes. You will find pages 10 and 12 of the following paper relevant:

http://citeseerx.ist.psu.edu/viewdoc...=rep1&type=pdf