We have been using the D programming language for GDTk development since 2015 and deriving a lot of benefit in terms of productivity. The tools and ecosystem are free (as in beer) for us to use. As a small way of giving back to the community, Peter Jacobs wrote a guest blog post for The D Blog that shares our experience using D to write large-scale simulation software.
https://dlang.org/blog/2022/02/02/a-gas-dynamics-toolkit-in-d/
Next time we write a post, we should probably simulate the hypersonic flow over the D logo to give some better physical fidelity for the representation. My inner aerodynamicist cringes at that uniform thickness shock layer in the logo.