Ansys Meshing – How to select internal walls?

Internal walls are the surfaces inside the domain that the flow meets on both sides: baffles, splitter plates, the wall of a tube separating two fluids. They are easy to miss because they are not part of the outer boundary of the model.

The mesher treats them differently from an external wall. A surface with fluid on both faces becomes an interior wall with a shadow face, and each side can carry its own boundary condition, which is exactly what conjugate heat transfer needs.

The practical advice is to name them in the geometry stage. A Named Selection created before meshing carries through to the solver as a labelled boundary, and saves you hunting for a hidden internal face inside a finished mesh.

In this tutorial you will learn two different ways to select the internal faces of a geometry. In this case we have a pipe with several elbows.