[lee_2017]

Dear Members,

is there an option within the Material Database to define the material properties depending on two variables? For example: density as function of temperature and pressure. I am using CCM+ version 13.02.

Example:

I would like to include this table as density function: Picture1.png

Is there any option? I searched for it but I found nothing.

Thank you!

[ashokac7]

Originally Posted by lee_2017

Dear Members,

is there an option within the Material Database to define the material properties depending on two variables? For example: density as function of temperature and pressure. I am using CCM+ version 13.02.

Example:

I would like to include this table as density function: Attachment 65856

Is there any option? I searched for it but I found nothing.

Thank you!

What type of density model you wish to use? Ideal or polynomial density. I see that density values are not varying by large number. Don't know why you are putting so much emphasis on that then.


If it is ideal gas, solver itself calculated the density for each cell based on temperature pressure data.


Explain more about this only then some valid comment can be done. Short questions may not get that much response. You can explain your question here.

[lee_2017]

Hello ashokac7,

Thank you for your reply.

As I mentioned in the post, it is an example. I used density but it could be also other properties like heat capacity or vicosity. The numbers in the table are also examples and invented by me in order to show the table I have. The real table is a big look up table from a standard and I would like to implement it into the material database of CCM.

I am specificly asking about material property depending on 2 variables because the polynomial just depends on one variable (as for example density in function of temperature).

It is not ideal gas, therefore I am using the mentioned standard look up table.

I didn’t find nothing about it in the manual, so I believe that such possibility doesn’t exist.

Regards

[ashokac7]

Originally Posted by lee_2017

Hello ashokac7,

Thank you for your reply.

As I mentioned in the post, it is an example. I used density but it could be also other properties like heat capacity or vicosity. The numbers in the table are also examples and invented by me in order to show the table I have. The real table is a big look up table from a standard and I would like to implement it into the material database of CCM.

I am specificly asking about material property depending on 2 variables because the polynomial just depends on one variable (as for example density in function of temperature).

It is not ideal gas, therefore I am using the mentioned standard look up table.

I didn’t find nothing about it in the manual, so I believe that such possibility doesn’t exist.

Regards

Yes. You can not give dependency on two variables.But if you see, as we specify density as polynomial in Temperature but temperature itself is not a independent variable. It will depend on pressure and what not.


I am not so sure about following statement but for sake of an argument,
Pressure effect will already be there in polynomial in T. As our temperature depends on pressure also. Please conform this with literature and also search for how to create this polynomial in T, and then there may be some idea on how to deal with multiple variables.

[me3840]

You can specify material properties based on two state variables. Just select the table(T,P) method under density in your physics continuum and give it the table.

Review the "Setting material properties methods" section of the user guide for more info.

[ashokac7]

Originally Posted by me3840

You can specify material properties based on two state variables. Just select the table(T,P) method under density in your physics continuum and give it the table.

Review the "Setting material properties methods" section of the user guide for more info.

@me3840 I don't find this option in single phase gas models. Though it is available in multi-component gas. Then how to use it in single phase simulation.

[me3840]

As long as you:
1. activate the user-defined equation of state
2. turn on compressibility under the user defined equation of state
3. activate an energy model (fluid temperature/enthalpy)

You can specify it as a dual table. You don't need multicomponent models.

Alternatively I'm sure you could use a field function to interpolate the table and specify it that way, but that may be limited to single lookup variables, my mind's a bit fuzzy.

[lee_2017]

Hello me3840 and ashokac7,


thank you for your help. With the question & answers I got it to work.



Regards

[LuckyTran]

Originally Posted by me3840

Alternatively I'm sure you could use a field function to interpolate the table and specify it that way, but that may be limited to single lookup variables, my mind's a bit fuzzy.

Although the original question was how to implement a density lookup table, I just wanted to point out that (in all versions of Starccm that I am familiar with) you cannot reference the temperature field in a user-defined field function. It's not a bug, it's a feature! You can define fields that are dependent on multiple variables, but temperature is not allowed (because it's too easy to make the solver break, it is forbidden). Not sure if newest versions permit this yet or not, probably not.


Anyway it's lucky on your part that you decided to use a density lookup table and managed to get it to work, because field functions would not have worked.

[me3840]

I'm not quite sure what you mean, you can certainly reference temperature in a field function. However perhaps you were trying to say for the state equation you can't choose which variables you wish to calculate via the function. i.e. the user defined equation of state table must output density, and temperature and pressure must be solved for. If you wished to output temperature instead, that would require them to rewrite some code I suppose.