Surface Part Guidelines

• Edges in two dimensional models cannot be used as surface parts.
• It is not necessary to assign a Surface Part material to surfaces that are walls. If a surface is on a solid part, it is a wall. If a surface is on an external boundary (no material on one side of it), then it is wall.
• Autodesk® CFD does not support a Surface Part material assigned to the external surfaces of a flow volume. (Some attempt this in an effort to simulate a sheet metal thickness.) Application of external heat transfer boundary conditions (such as heat flux and film coefficient) is also not recommended. The reason is that Surface Parts that are on external boundaries are not completely incorporated into the calculation--their material and thickness information will not be included. Because of this, there will not be a thermal gradient calculated across external Surface Parts. An alternative to applying Surface Parts for external wall surfaces is to leave the external surface unspecified, making it a wall by default. When this is done, externally-applied heat transfer boundary conditions will then be properly incorporated into the simulation.
• Multiple layers of material cannot be represented by applying multiple layers of Surface Parts. To represent a laminate of thin materials, apply a single Surface Part material that uses an effective thermal conductivity based on the conductivity values of the laminate materials.
• Surface Parts must be completely enclosed in a 3D volume. Surface Parts cannot extend outside of the 3D model.
• It is not possible to change the mesh on a model containing surface parts and continue the analysis from a saved iteration. When the mesh is changed, the analysis must be started back at the beginning (iteration 0).
• Surface parts must not contact parts that are extrusion meshed.

CAD-Specific Guidelines

Autodesk® Inventor

A convenient way to include Surface Parts is to create a 3D part with the surface shape of the desired Surface Part.

Mesh the volume as a fluid, and assign a Surface Part material to the surface, as described in the preceding section called Surface Parts on Surfaces of Volumes.

Pro/Engineer

Surfaces that are to be Surface Parts should be created as separate parts and added to an assembly consisting of the surrounding flow volume part and any other Surface Part and 3D parts. If a Surface Part is included as a quilt feature in a part, the part may either not come into Autodesk® CFD correctly or it will incur meshing difficulties. Also, Surface Parts must not interfere, and must not cross one another. Multiple Surface Parts can meet along an edge, however. Surface Parts that are not connected (completely disjointed) must be created as separate parts, and included as components in the assembly.

Note that quilts are not supported when launching with the Granite launch method.

Solid Works

Surface Parts can be created as either separate parts in an assembly or as surface features in a 3D part. Surface Parts can interfere with one another, and disjointed surfaces can be included in the same part.