# Get IDs of group of Faces

Hi,

I'm trying to automate the generation of a mesh with Salome. I have made a script that generates a parametric geometry, defines some groups and then generates a mesh for CFD purposes. I need to add a **viscous layer** hypothesis for which I'd like to use the function **SetFaces**, where I pass the walls defined in the geometry. If I dump the study I get something like

ViscousLayers.SetFaces( [ 7, 12, 20 ], 0 )

As I am not completely sure that in every possible parametric geometry the number and the ID of the faces will always be the list [7,12,20] I tried to access that list with some functions, but without success. As it can be seen in the attached image, I have a group named *wall1* made of 3 faces, whose indices are [7, 12, 20].

I tried to use:

ViscousLayers.SetFaces(wall1.GetSubShapeIndices(), 0 )

but wall1.GetSubShapeIndices() returns [7, 12, 17] instead of [7, 12, 20] and obviously the mesh generation doesn't work as expected.

What is the correct way to access the indices of a group of faces?

Thank you

Claudio

Hi Claudio

You can directly use your geom group to define Viscous layers by calling `ViscousLayers`

() method of your 3D algorithm.

Best regards

Edward

Hi SMESH expert,

thank you for the links. I had read them but I didn't find exactly what I was looking for. Nevertheless, reading the code again made me understand the mistake. I made a Fusion of two objects in the geometry, keeping the groups of the original shapes, but in the MESH module I pointed to the groups of the original objects. That explains the difference in the list of faces.

Once I point to the right name, wall.GetSubShapeIndices() or geompy.GetObjectIDs(wall) give the expected results.

Thank you

Claudio