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Paul August 16, 2004 10:14

Multiphase flow modeling
Hi guys,

I want to use Fluent to simulate multiphase flow. My work may involve in significant model modifications usig UDF. I want to have a clue of how user-friendly to use UDF and how powerful they are.

Your information is very helpful and highly appreciated.


thomas August 16, 2004 12:59

Re: Multiphase flow modeling
I would say handling udf for multiphase modelling isnt an easy thing. For me the only difficulty is to understand the notion of Thread and how to get them. There i am assuming you already know how to use udf for a single phase flow. About how powerful they are, it exist some limitation depending on how complex is you model modification ... let us know precisely what you want to do and me or somonelse will tell you what is up with your problem.

Paul August 16, 2004 13:20

Re: Multiphase flow modeling
Thanks Thomas,

Actually I don't have any experience of udf. I have been using CFX quite a lot and just tried several simple cases in FLuent. For example, if I want to simulate the entrained droplets interacting with the gas and liquid phases in stratified or annular flow. In this case, addition of a source or sink term both in the continuity and momentum equations is necessary to describe the mass and momentum gain or loss of the liquid phase, as well as the generation of the liquid droplet phase. Of course, it is not practical to tracking the individual droplets with the computer power till date. Also, the mass and momentum interchange coefficients should be functions of local flow parameters. Meanwhile it may also necessary to modify the drag force and lift force which are believed to be functions of local void fraction. I am well aware the model modification for this kind of work is extremely intensive. I want to get a feeling of the possibility of accomplishing this work using FLUENT.

thomas August 16, 2004 14:22

Re: Multiphase flow modeling
Your problem seems to be manageable with fluent. Computing the mass and momentum interchange coefficients, drag and lift force functions of local flow parameters isnt a problem using fluent ... read carefully the documentation. The only difficulty i see is how you are gonna create the droplet generation. This cause a stratified flow or annular flow is relevent from teh OVF model when the a droplet tracking is relevant from the DPM model or euler euler model in certain case. All that depends on what you looking for in the end ... this will tell you what assumption to make and thus what model to use. Hope this help

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