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Old   November 20, 2015, 10:50
Default internalField condition
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Tiko
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Hi Folks,

In the bubbleColumn tutorial of multiphase flow, they have used
internalField nonuniform List<vector>
1875 scalars for alpha
and 1875 vectors for Ua and Ub.

Would anyone tell me where did they get the scalars and vectors from? ( i didnt find them in the PolyMesh folder). Also, i would like to know what is the difference between
internalField uniform ( 0 0 0); and
internalField nonuniform List <vector>

and the difference between
internalField uniform 0; and
internalField nonuniform List <scalar>

Thank you,
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Old   November 20, 2015, 11:11
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Joćo Ferreira
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Hi,

internalField uniform (0 0 0) - with this you define that all the internal elements of the mesh (not boundaries) have the value (0 0 0). The same applies for a scalar value.

internalField nonuniform List <vector> or <scalar> - you can set a list of values for the internal elements of the mesh. For example, for the velocity field, if you know its distribution you can use it by setting this type of list. The number of entries of the list is the number of internal elements that your mesh has.
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Old   November 20, 2015, 11:14
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Quote:
Originally Posted by jmdf View Post
Hi,

internalField uniform (0 0 0) - with this you define that all the internal elements of the mesh (not boundaries) have the value (0 0 0). The same applies for a scalar value.

internalField nonuniform List <vector> or <scalar> - you can set a list of values for the internal elements of the mesh. For example, for the velocity field, if you know its distribution you can use it by setting this type of list. The number of entries of the list is the number of internal elements that your mesh has.
Hi Joao,

So the entries are random numbers i choose them, or i get them from a certain directory.
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Old   November 20, 2015, 11:27
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I'm not familiar with the tutorial you mentioned, although the alpha and U values are probably an initial distribution of the field in the internal elements.

For example, if you use the potentialFoam it will give you an initial "guess" of the velocity field on a certain case. Which is then used by the other solver you are using to solve the case.

I don't think you can find those values in any directory. Those values can be either obtained by using another solver or are known from the start.
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Old   November 20, 2015, 11:30
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the point is that there is 1875 values for both scalars and vectors, So i dont think i have to set them by guessing
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Old   November 20, 2015, 11:38
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Obviously you don't have to guess them, remember that it's a tutorial and so it's ready to be solved.

I was trying to explain the difference between the uniform and nonuniform entry on the internalField, as I said i'm not familiar with that tutorial.
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Old   November 20, 2015, 11:48
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i see. It seems that you have a strong background about internal and boundary conditions, So i would like to ask if you can help in this case. I am trying to model a multiphase case study. i have two flows from two inlets. in the simulation, i need to see two flows coming from two inlets and leaving from one outlet. what would be the boundary conditions?
Meshing parts( inlet1 , inlet 2, walls, and outlet). constant velocity at inlet1 and changing velocity for inlet2 and changing velocity of the mixture at the outlet)
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Old   November 20, 2015, 11:53
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Jao, here is the model
Attached Images
File Type: png Guru Pic.PNG (22.0 KB, 10 views)
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Old   November 23, 2015, 07:10
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Joćo Ferreira
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Hi,

I can try to give you some guidance, although my experience with two phase flows is not that big.

If you give me some more time I will give you a more information, I am having a lot of work at the moment.

Anyway, as far as I understand you need to define the properties of both fluid on the constant folder in separate files.
To define the boundaries, you need to create a file for each phase. As you can see on the tutorial you mentioned, you have two different files for several field (*.air and *.water). So, try to create these files for the two different phases you have.
The inlets, for example, if you want air to enter on "inlet1" you define it on the "U.air" and on the same inlet, but for the other phase, you define it as zeroGradient.

I am not totally sure if i'm correct because I need to look into the tutorial with more time.

I suggest you to try what I said and maybe sent me your case so I can have a look. Anyway, I will try to give a more complete answer as soon as I have time!
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