Reply To: “Converting a 3D channel into a duct”
For a duct another case, e.g. turbulence/nozzle3d might be a better starting point. For the channel case the first step will be to remove the periodicity towards the sides of the domain (see the call to CuboidGeometry::setPeriodicity in line 413) and set other boundary conditions on the resulting walls.
If you describe your desired setup in more detail we will be able to provide better guidance.