I think of how many days it took to simulate much simpler things back in the 1990s on an IBM Unix workstation
That said, there does tend to be a few differences between graphics-oriented fluid dynamics simulations and simulations that actually have to obey physical laws to high order precision. 
Conservation of mass and momentum is a good start, but the GPU Gems treatment of the Navier Stokes equations is … breezy …
The results are really pretty, but based on the references you might find the approximations to the physics to be first order.
