Volumetric source term missing - Syrthes/CS coupling

[JeremyA]

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

[JeremyA]

Here's more files

[JeremyA]

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

[Yvan Fournier]

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

[JeremyA]

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

[Yvan Fournier]

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

[JeremyA]

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

[Yvan Fournier]

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

[JeremyA]

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