[saiguruprasad]

Hey,

I am trying to do Conjugate heat transfer using ANSYS Fluent.

I have a solid plate with fins on it. I have a solid-fluid-solid-fluid-solid region.

I have no inlet or outlet and have periodic boundary conditions in the streamwise and transverse directions (like DNS simulations). The temperature in the first fluid region is 875 K and the second is 675 K, but I am unable to specify this. There is only one periodic conditions option in Fluent, which sets the conditions (mass flow rate or pressure drop, and temperature of the fluid for the periodic domains).

I would like to define two different periodic conditions (different mass flow rates and temperatures). Is it possible? If it is possible, I would like to know how to do it.

[vinerm]

Are these periodic regions separated by a wall? Could you share a snapshot or schematic of the domain?

[saiguruprasad]

Yes. The periodic domains are separated by a solid region. I have attached an image of the domain.

[vinerm]

I am afraid that's not doable, not with standard options.

[saiguruprasad]

Is it possible to do this using some UDF or any other way?

[vinerm]

Yes, you can use UDF to do this. You have to connect profiles of the boundaries that are supposed to be periodic.

[saiguruprasad]

Can you provide some more details.

I don't actually want to connect the two fluid domains. The top fluid domain is a periodic domain and the bottom fluid domain is another periodic domain. I can create them in fluent by creating interfaces.

I would like to know how to specify different flow rates in top and bottom fluid domains and different temperatures also.

[vinerm]

You can make one of the domains periodic and use periodic conditions for that domain. You can create periodic domains directly without interface provided the mesh on both periodic boundaries is same within a certain tolerance.

For the other domain, you have to write a UDF.

[saiguruprasad]

Can you provide some tips on writing UDF for periodic domains?

I am using non-conformal periodic boundary conditions. I would like to know if it possible to write UDF for non-conformal periodic boundary.

[vinerm]

Conformal or non-conformal don't matter much, except that you will have to do interpolation in case of non-conformal. For conformal, you can do 1-to-1 mapping. Since periodic condition is nothing more than implementation of same values of field-variables at both periodic boundaries, following algorithm could work

1. Use DEFINE_ADJUST to extract values for all fields, such as, velocity components, turbulence quantities, non-dimensional temperature, etc. at one of the boundaries. This boundary could, preferably, be set as pressure outlet.
2. Use DEFINE_PROFILE at the other boundary to apply these profiles. Since the boundaries have non-conformal mesh, you will have to interpolate the field data before applying. You will need as many DEFINE_PROFILE functions as many field variables you want to apply the condition for.

If you are comfortable with UDFs, then you can use Profile structure of Fluent to do the same. It's more sophisticated and you will not need interpolation; Fluent will do interpolation on its own.

[Weixigggg]

I've been using "system coupling" recently to try to solve this problem. However, "system coupling" cannot establish connection between two Fluent