Merge Faces
The operation merges faces within a given maximum distance by collapsing the space between the selected faces, as shown in Figure 7-96. This means that you, for example, can bridge gaps between different parts of the geometry using this operation.
Figure 7-96: Merging two faces (blue) to collapse the gap between them. The result is shown to the right.
Thin gaps can result in only partial or no connection between parts. Perfectly touching parts are usually wanted for most physics simulations. A gap can also result in narrow domain regions if there is a surrounding air domain or similar. This will require a very fine mesh to be well resolved. Merging the faces adjacent to the gap will remove the thin narrow domain region and therefore the need for a fine mesh.
To use the operation, in the Geometry toolbar, from the Virtual Operations menu (), select Merge Faces (). Then enter the properties of the operation using the following sections:
Face Pairing
Use the setting Pairing of faces to keep and remove to specify how to input the faces to merge. Select Automatic (default) to select all faces to merge in one list and let the software decide which faces to keep and which faces to remove. Select Manual to manually select the faces to keep and then select the faces to remove, using the sections below.
For Pairing of faces to keep and remove set to Automatic, click the Active button to toggle between turning ON and OFF the Faces to merge selection. Select the faces that you want to merge in the Graphics window or add them from the Selection List. They then appear in the Faces to merge list.
For Pairing of faces to keep and remove set to Manual, click the Active button to toggle between turning ON and OFF the Faces to keep selection. Select the faces that you want to keep in the Graphics window or add them from the Selection List. They then appear in the Faces to keep list. Then, click the Active button to toggle between turning ON and OFF the Faces to remove selection. Select the faces that you want to remove in the Graphics window or add them from the Selection List. They then appear in the Faces to remove list.
Maximum Distance
Use the setting Maximum distance setting to specify the maximum distance to bridge when merging faces in the geometry. Choose Relative to enter a value in the Relative distance field. This value is relative to the length of the longest side of the geometry’s bounding box. Select Absolute to specify a value in the Absolute distance field. When the operation is built with the setting Automatic (the default), the value in the Absolute distance field is automatically updated to correspond to the actually used distance. The automatic tolerance is based on the size of the bounding box of the mesh.
Face Matching
The contents of this section differ depending on the setting Geometry representation in the Settings window of the Geometry node.
COMSOL Kernel
Select the checkbox Force one-to-one to force the faces on the remove side to be matched with the keep side without any imprints. This is useful when the shape is approximately the same and you want to match them exactly. Note that if the faces have too different shape, the merge will generally not be successful with this option.
CAD Kernel
Use the Method setting to specify the way to match a determined pair of faces to keep and remove. The method Make imprints means that the faces to keep make an imprint on the faces to remove and, symmetrically, the faces to remove make an imprint on the faces to keep. Then, only the overlapping imprints are merged. This is shown in Figure 7-97.
Figure 7-97: Merging faces by making an imprint on the bottom surface of the upper part.
Use the Precision field or slider to specify the accuracy of the imprint. A low precision will give a sloppier matching, meaning that face regions with approximately the same shape will be matched without imprinting, while high precision gives a more accurate imprint but also means that small faces and details can appear.
The method One-to-one forces the faces to remove to be matched with the keep side without any imprints. This is useful when the shape is approximately the same and you want to match them exactly. Note that if the faces have too different shape, the merge will generally not be successful with this option.
Resulting Finite Voids
The Create domains checkbox is selected by default to create domains from watertight void regions. If you do not want or need domains, clear this checkbox.