Learning Forum

[DannyOuk]

Hello, nI am currently working on modelling a multiphase flow system in FLUENT with water as the primary phase and two phases for air (which are differentiated by bubble size) . I am trying to model mass transfer between the two phases of air using user-defined functions (UDFs). nMy first question: Is there a difference between modeling mass transfer terms through the Phase Interaction menu as opposed to applying source terms to the two air phases in the Cell Zone Conditions menu? Is either version preferable to the other? nSecond question: I know that these two different methods result in a slightly different writing for the UDFs (different macros: Define_Mass_Transfer vs. Define_Source). However, when using the source term method, I had two source term UDFs (1 UDF for each group). But if I apply mass transfer terms through the Phase Interaction menu, do I need only 1 mass transfer mechanism that acts as the net sum of mass transferred from group 1 air bubbles to group 2 air bubbles? nThanks for all your help! nSincerely,nDannyn

[DrAmine]

1/Preferable to use UDF with DEFINE_MASS_TRANSFER or the linearzied version of it. Only one is required whereas for the cell zone source terms you require more..n2/Why not using Population Balance here for the air phasesn

[DannyOuk]

Thank you! I'm currently trying to model this system using interfacial area transport equations rather than the population balance models. nSincerely, nDannyn

[DannyOuk]

Hello, nI'm currently trying to apply a mass transfer UDF for this system. Is there any benefit to using the linearized mass transfer UDF terms? nI have applied both types and both seem to have great difficulty reaching convergence. nSincerely, nDannyn

[Rob]

I think linearised is more stable, but other than looking in the mass transfer section of the manual I'm not sure. n