First of all try to get the latest version this helps a lot for mass flow calculations.
Next to that try to make your tube longer and plot streamlines sometimes they are re-entering the surface (when a object is disturbing the flow) maybe this can have an influence on the mass flow calculation?
Next to that try to make your tube longer and plot streamlines sometimes they are re-entering the surface (when a object is disturbing the flow) maybe this can have an influence on the mass flow calculation?
