Warning—Shell Elements Defined on External Surfaces
The following warning is issued for a model that contains surface parts (shells):
Warning: Shell Elements Defined on External Surfaces
This issue occurs when Surface Parts are assigned to an exterior wall surface. (It is a non-fatal warning, so the analysis will still run.) Such surface parts will be ignored; there will not be a temperature gradient computed across them. This is because the surface part does not have duplicate nodes and no virtual thickness.
This warning is also issued when an internal surface part (such as between two solids) is meshed so coarsely that there are no nodes on the surface. All are on the edges of the surface part. Autodesk® Simulation CFD cannot duplicate the nodes of the surface part, and the resulting temperature distribution through and across it will be incorrect.
There are two primary ways to resolve this issue:
Remove surface definitions from exterior surfaces.
Apply a smaller element size to the surface part to ensure there are nodes on the surface.
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