I helped develop a hydro solver coupled with radiation at Los Alamos this summer. We observed from 7x upto 15x performance improvement on a single GPU compared to 64-core intel CPU. [1]

Now granted, the flops to byte ratio for this program might be better than an avg fluid simulator. Also, our performance tanked when we moved to multi-node system. But I am aware of underlying reasons behind the scalibility issues and they don't feel like problems that can't be overcome.

[1] https://github.com/lanl/HARD/tree/main