Error in MFiX results

Hello,

From the paper titles you provided, i find that we may have the same research topic. I am recently studying bubble properties based on TFM simulation. But, the validation of simulation is not what i really care about now, though i think it is really important. I am still confused about how to calculate bubble velocity, or rise velocity. I asked the relevant questions to Weber, but there is still no answer. Do you have any ideas about this problem?