Hello,
It looks like there’s a small confusion on how volumetric passive scalar sources interact with velocity inlets.
This is what you can infer from the inlet boundary condition:
The volumetric scalar source will remove scalar from the domain based on their volume. Each one of the 1m3 boxes will remove 200 mL/s, to be more precise. So a setting of -200 doesn’t mean that the scalar level will be bounded between 400 and 400-200 = 200.
In the aftermath, from the initial 28000 mL/s of contaminant that enter the domain through the inlet, 1000 mL/s are removed from the domain via the 5 “scalar sinks”, and the rest exits through the outlet.
This public project that I posted some years ago may be insightful: Passive scalar volumetric source - General setup and Paraview T1 conversion by Ricardopg | SimScale
Cheers