Learning Forum

[Golaselo]

Hello everyone, I am moddeling Jet Impingement Heat Transfer in the pipe (2D). I know I have to modyfiy the energy equation to include element responsible for turbulent heat flux. Can anyone help me with this, give some tips?

Best regards, WG

[aitor.amatriain]

Turbulent heat flux is included by default when a turbulence model is used. If you need to include a different term than the "typical one" (i.e., with a turbulent thermal conductivity), please post the expression here.

[Golaselo]

Hello Aitor, could you help me with modyfying energy equation in Ansys?

[aitor.amatriain]

Which term do you need to include?

[Golaselo]

Hello, in picture, there is my energy equation from my professor. I need to include term responsible for turbulent heat flux. I am using k-epsilon and k-omega models for turbulence in my flow (2D Pipe).
The last term on that equation "-ujO"

[aitor.amatriain]

Assuming that a is constant, I would say that the correct expression of the energy equation is as follows:
This is the equation that is implemented in Ansys Fluent. What is your closure for the turbulent heat flux? The typical approach for the turbulent heat flux is based on introducing the turbulent thermal conductivity, and in that case you do not have to do anything, as it is implemented by default.

[Golaselo]

So, to summarize. I am using standard energy equation in fluent and when I use any kind of turbulence model (k-epsilon and k-omega in my case) this term (the last in equation) is included in it. Is that correct?

[Amine Ben Hadj Ali]

Yes.

[Golaselo]

Hello again, could you tell me how to write an UDS for implementing anisotropic turbulent heat flux? I read it from this article.

https://www.epj-conferences.org/articles/epjconf/pdf/2015/11/epjconf_efm2014_02063.pdf

[Amine Ben Hadj Ali]

Fluent does offer a way to define anisotropic UDS diffusivity.

[Golaselo]

yes, I would like to get turbulent heat flux with turbulent thermal conductivity. I got information from my professor that I have to write an UDF to get that. It is possible to calculate it in another way, but I have to get turbulent heat flux directly from ANSYS by using UDF, could you give me some advices?