Need benchmarks for freespace vortex method
 

I have implemented a free space ( no boundaries ) vortex method (incompressible, 3D flows) and I am able to simulate things like vortex rings, their collision ...

I am looking for some benchmarks/analytical solutions that I can use for validating my program. Note that it does not support boundaries at the moment and can only solve for an initial vorticity distribution in free space.

Check this

http://zjw.public.iastate.edu/hiocfd/case_c1.6.pdf

Thanks praveen. However, I am looking for 3D flows and the link discusses a 2D problem.