How to correctly measure the mass flow rates in a two phase flow?
I have a problem. To make a long story short – I don’t know to properly measure mass flow rate in a two-phase flow with VOF method.
I have such a situation. Rectangular domain 5m height, with an air issued from the central nozzle and coflowing stream of water at a constant temperature.
I measure the inlet mass flow rates using the option in Surface Report menu. The signals of mixture mass flow rates measured at the inlet are OK and correspond to the inlet mass flow BCs, i.e., 1kg/s of water and 0.3 kg/s of air.
But look at the values from the planes which are respectively 1m, 2m, 3m far from the inlet. The values of mass flow rates are fluctuating considerably and even the averaged values are far from the inlet mass flow.
What am I doing wrong? How should I monitor the mass flow rates of the phases to get correct values, equal to that at the inlet?
Thank you for any advices.