[hmdl]

Hi everybody,

I am running a multiphase flow where particles are injected in a free jet. In order to model the melting of discrete particles I used a User Function for the Specific Heat in material properties of discrete particles. It worked fine a week ago... But now CFX complains that I cannot use a User Function for Specific Heat field. I am attaching the screenshots. I'm sure there is a silly mistake somewhere, can someone maybe see what I'm not seeing ?

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[ghorrocks]

The error message is very clear - your available options are listed. If you say your function of temperature worked previous, well I cannot explain that.

[hmdl]

In CFX everywhere where you can enter a Value you can also enter an Expression or a User Function. An Expression still works, but for some reason Temperature dependent Interpolation data doesn't.

[hmdl]

It turnes out Specific Heat doesn't accept any kind of interpolation data, not just temperature dependent. Anyone has an idea what would cause this ?

[ghorrocks]

In CFX everywhere where you can enter a Value you can also enter an Expression or a User Function.

No, this is not correct. There are many places where you are restricted in what you can make functions of what. You have found an example.

Anyone has an idea what would cause this ?

It is because when you have variable properties like this it introduces all sorts of cross terms and high order terms. It is not a simple substitution of a constant with a function of temperature. The underlying equations in CFX have not got all combinations of these higher order terms included - there is a limit to have many permutations of all the options the software can support. So the high order terms associated with Cp as a function of temperature for particle have not been included, so the solver stops you from generating functions which do this.

You best option is to see if one of the supported options can be made to fit the Cp curve you are trying to implement. You might be able to get the zero pressure polynomial or NASA polynomial to fit your data.