Advection equations with the incompressible swirling deformation flow 
described in 

@article{rjl:advect,
  author="R. J. LeVeque",
  title="High-resolution conservative algorithms for advection in
  incompressible flow",
  journal="SIAM J. Numer. Anal.",
  volume="33",
  year="1996",
  pages="627-665"
}