how to implement a boundary conditions on multiphase boundary in fluent?

anshsanshs Member Posts: 28

I'm having a bucket filled with water and oil on top of the water at high temperatures. That makes the problem with 3 phases (water, oil, and air). oil on top of the water and subsequently air on top of the oil. Schematic as shown below ( Phase ID: Blue = air, red = oil, green = water )

I use 'patch' for marking different phases on the cell zone.

I want to apply a boundary condition on the top surface of the oil layer, i.e at the oil-air interface.

e.g = Temperature radiation BC, air above is at 300K and Oil is at 500K.

Thus a mixed temperature boundary condition : (I) Radiation with external emissivity 0.7, so that heat dissipates to the ambient air, (ii) Convection with h= 20 W/m2 on the oil-air interface.



  • KremellaKremella Posts: 2,497Admin


    If you are solving this as a multiphase problem, the oil-air interface is not a flow boundary, and therefore, you cannot apply a boundary condition there. Boundary conditions can be applied only to the external boundaries of your computational domain. If you are solving this as a Multiphase problem, the heat transfer between the oil and air phases (especially at the interface) will be accounted for by the solver when you solve this model. You don't need to explicitly specify conditions on this interface.


  • anshsanshs Posts: 100Member

    Thanks for the reply Karthik,

    Yes, I'm solving this as a Multiphase problem!

    1. Now how may I tell the solver that the external emissivity which is arising from the oil layer into the air is 0.7; ( will it depend on the radiation model?)
    2. And which radiation model shall I use for the best results? Do all the radiation model will have the features to cater to my requirements (as shown above)
    3. Can I also know, what fraction of the total heat dissipation from the oil-air surface is that of radiation?

    Thanks again,


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