Ashish Khemka
Ansys Employee
Hi @DannyOuk, ,nResolving this post as it is a duplicate one. We are answering your question here. n

Hello,I am currently using a multiphase flow simulation in ANSYS FLUENT with flow inside an annulus by modelling a 2D axisymmetric geometry. I was trying to model boiling of water using an Eulerian boiling model while incorporating two vapor phase groups. The two vapor phase groups are meant to account for differences in the types and sizes of bubbles. After having group 1 steam bubbles formed by boiling, I would then apply interfacial area concentration models to model the coalescence and breakup of the bubbles (which would result in mass transfer between group 1 and group 2 bubbles). This means that there would be two materials for the fluids (water-liquid and water-vapor), but there should be three phases (water, steam-group-1, and steam-group-2). Earlier, I was able to apply this three field methodology with a water-air mixture, which had interfacial area concentration modelling but no boiling models. However, when I tried to do this with a water-steam mixture with boiling for the phase changes, I run into a few errors. I can apply the boiling models in a two-field model with only water and one group of vapor being modeled, but adding the third phase results in this error when I run the calculation: Error at Node 0: The primary phase must be the liquid phase!Do you have any clue as to why this happens and how I can fix this error? The primary phase is already marked as liquid water with the secondary phases being marked as water vapor. Currently I only have boiling mass transfer for water to group 1 vapor and I plan to model group 2 vapor formation from coalescence of group 1 bubbles. Thanks for any help you can provide!Sincerely,Danny

I'm closing this post.nRegards,nAshish Khemkan