hello I want to know what is the threshold value of the dispersed phase volume fraction for which the mixture model remains applicable. My mixture is gas bubbles dispersed in water. The gas becomes a continuous phase in some regions of the domain. The inlet volume fraction can vary from less than 5% to more than 70%. Thanks.

i'm doing a similiar work where the dispersed phase is water. in your case, you should faced to numerical stability matters. i found that the default drag law in fluent is not the best one for our kind of flow. i advise you to choose a symmetric drag law(define->phases->interactions). in fluent documentation, you can read why this law is appropriated. however, the system doesn't became convergent if the volume fraction is to high. in this case, you should reduce under-relaxation number of volume fraction. but, do not reduce is drasticly, because fluent doesn't calculate if it's to small. ( divide the number by 10, it should be suffisant).

i wish i helped you. send me an email, if you want more details.

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I am also working on mixture model for slurry flow simulation,( water and sand ( 0-5% vf)). I am not able to get simulations converge correctly. I am new to Fluent.Can you assist me in my case ?
Thanks in advance .