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Parshant Dhand November 14, 2003 12:48

Two Phase Flow
Hi there,

I wnated to know how can I set water vapor + Liquid water coming in from one boundary inlet. My Problem has two inlet and one outlet. On one inlet there is air coming in and other inlet there is water vapor with vapor fraction of 0.74 coming in. How do I model the stream with liquid water and water vapor coming in. Thanks


ccc November 14, 2003 13:27

Re: Two Phase Flow
hi, Parshant

your problem is interesting. I have one point unclear. Does the water in the water vaper will condense into the liquid water.

If the answer is FALSE, i think the simple two phase model will work. however, in the case of TRUE, it is a little complicate. The first solution came into my mind is to use udf to add or subtract a source in the continuum equation.

thomas November 14, 2003 15:58

Re: Two Phase Flow
Hi, A multiphase model will allow you to model your system. Knowing the water-vapor bubble size, volume fraction,and the speed velocity of each phase, you can set you inlet condition. For your only air inlet just set the volume fraction to 1, velocity water =0, velocity air = ... The euler-euler model seems to be the most adequat


mateus November 15, 2003 03:06

Re: Two Phase Flow

Try it with mixture model first - it works faster since it doesn't solve equations for each phase. If you don't get good results switch to Euler-Euler model...



thomas November 17, 2003 12:51

Re: Two Phase Flow
Thanks for your message for Two Phase flow it was useful, can you please tell me how do I get to know the bubble size for the liquid water and water vapor for phases. Thanks Parshant -----------------------------------------------

Check publication about the same kind of simulation or problem. If you do not find that, I would suggest to use a bubble size to avoid special effect due to bubble deformation (change of drag coefficient, Lift, ....).

Hope this help. thomas

Alamgir November 18, 2003 21:37

Re: Two Phase Flow

I'm also modelling such type of problem. I think Multiphase Mixture model is well enough to model. Specify each inlet separately (inlet1 and inlet2) then in Fluent choose 3 differnt materials (water vapor, water lq and air). Now which is primary phase? Set it first with knowing velocity at bc. Then set secondary phases with volume fraction and velocities.


nitish November 19, 2003 09:50

Re: Two Phase Flow
i'm working on the vortex air separator using FLUENT. in case of 2 phase flow (inlet=air+20% liquid air fraction), what model can be used to get the extent of separation?

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