Reply To: What does Resolution mean?
The N value passed to the unit converter is the number of cells per physical reference length (which is also managed by the unit converter). The resulting physical discretization width is then passed to e.g. the cuboid geometry.
There is no general answer to which value one needs for an application. It really depends on what you are doing.
You can view the resulting geometry in the VTK output (also without calculating any timesteps).
There you will also see why you get the “Discrete normal is not valid for interpolated pressure boundary” error – likely the inflow (?) where you want to apply the velocity boundary is not resolved enough for the selected value of N.
In case you did not see it yet: We also have a user guide [PDF] where the basic usage of OpenLB is detailed.