Hi @1318980!
I think the gravity direction is right, although you probably spotted my mistake. See if it makes sense:
The orientation of the geometry is this one:
So, the gravity direction should, indeed, be pointing to -y. But, when I was setting the pressure inlet and outlet boundary conditions, I thought they had to be assigned to the lateral faces, which were the ones that had been set as the velocity inlet and pressure outlet in the forced convection simulation. Seeing the results now, and the temperature distribution, I think what you meant to say before was that I needed to assign these pressure boundary conditions to the top and bottom faces, right?
Best regards,
Gabriel