looks like periodic boundaries still have issues with Navier Stokes
I attach here an example, a rectangular pipe filled with air with a body force along its axis (Z axis), a no slip boundary condition on sidewalls, and a periodic boundary condition on inlet/outlet.
After running the solver for a steady state solution with the Smagorinsky turbulence model, I see antiperiodic x and y velocity on inlet and outlet (also pressure is antiperiodic).
Is it a bug?
![Image](https://preview.ibb.co/gFNkQk/inlet.png)
![Image](https://preview.ibb.co/cBqTd5/antiperiodic.png)
![Image](https://preview.ibb.co/iB3TT5/outlet.png)
Don't care about values, It's just a qualitative example