code_saturne User's Forum

Hello,

I am using Salome CFD 8.5 for Scibian

I am trying to do a coupling of an heatrod (2 solids) inside a cylinder full of air
When I do some tests only on Syrthes, I succeed to simulate the volumetric source term inside the first solid of the heatrod (the wire) (despite I had some difficulties here too)

But when I do a coupling calculation, this volumetric source term is no longer took into account
Could you check if I am doing it right ?

Thank you very much

Jeremy

Here's more files

I think I have just understood where the issue is :

my system is 2D axisymmetric

When I impose a Surfacic flux or Volumetric source term by using Syrthes alone, I got no issue

But if I want to do the same in coupling calculation, they are no longer took into account

Do you know why and how I can avoid this issue ?

Best regards

Jeremy

Hello,

If you are doing a volumic coupling, you need to define it in code_saturne using a user subroutine (see cs_user_coupling.c and associated examples), as the GUI only allows the definition of surface coupling (and using a 2D projection, a surface is considered a volume in the "original" space).

You did not post any user subroutines. Are you missing this part of the setup ?

Regards,

Yvan

I think I have a surfacic coupling, between the heatrod and the fluid, right ?

In Salome, my Solid is 2D and my fluid domain is 3D with 1 cell size following Oz

What is the difference between surfacic and volumic coupling btw ?

Thank you

Jeremy

Hello,

Volumic coupling is used for volumes that are both fluid and solid (i.e. zones with some form of porosity or cluttered regions, containing both fluid and solid portions, at a level of detail smaller than the mesh resolution).

Surface coupling is used for the classical cases where a surface separated the fluid an solid parts.

When going from 3D to 2D, (i.e. projecting to a 2D surface), the logic is the same, but volumes become surfaces, surfaces become edges.

Regards,

Yvan

So I have a surfacic coupling for my case

But volumetric source term or surfacic flux in Syrthes are not took into account when I try coupling
In regards to the files i sent to you, do you have any suggestion to solve this problem ?

Thank you very much

Jeremy

Hello,

I do not know if you used the correct groups for Syrthes. The groups in the solid mesh seem strange, and a little complex relative to a simple mesh, but I assume the Ext_cera group matches the "Int" fluid faces.

Since the Syrthes tools provide a mapping from group names (or family ids) to Syrthes "colors" in a separate file, I would need to check that file to be sure. Could you post that ?

Regards,

Yvan

Hello Yvan,

actually I understood one part of my issue :

time step for natural convection is very low, and strangely my heatrod needs 3 hours to heat (radius <0.01 m)
So to do coupling, I have to do a lot of iterations with a minimal time step, and I haven't done that yet
That explains my issue

To solve it, I do a first coupling calculation with a large time step (10s) to let my heatrod heating
Then I restart the simulation with a low time step for natural convection

It's working

HOWEVER, I don't understand why it is needed 3 hours for my heatrod to heat ...
Could you check that pls ?

Thank you

Jeremy