Proximity Size Function Sources determines whether regions of proximity between faces and/or edges are considered when proximity size function calculations are performed. This option is available only when Capture Proximity is set to Yes. You can specify Edges, Faces, or Faces and Edges:
Faces - Considers face-face proximity between faces. Face-edge and edge-edge proximity are not considered (that is, the trailing edge of fluid around wings will not be captured with this setting).
Faces and Edges - This is the default for part/body-based meshing methods. Considers face-face and edge-edge proximity. Face-edge proximity is not considered.
Note:
In cases involving face-face proximity, the face normal orientation is ignored during the proximity calculation.
It is important to resolve all edges as much as possible for better feature capturing and for minimizing the occurrence of non-manifold nodes. For this reason, you should specify a setting of either Edges or Faces and Edges. For many models, the Edges setting may be sufficient to resolve all proximity situations. For large complex models, using either the Faces and Edges or Faces setting may result in longer computation time.