Limitations of the ALE Method

The following limitations apply to the ALE method in general and therefore to the Moving Mesh and Deformed Geometry interfaces:

•	The connectivity of the mesh remains unchanged during the mesh deformation, which means that topological changes in the geometry are not allowed.

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When the mesh deformation becomes large, the quality of the mesh created by the smoothing equations can deteriorate, and the solver might then run into convergence problems. Sometimes an Inverted mesh element warning displays in the Progress window for the solver, which means that a mesh element has (partially) warped inside-out. The solver might even stop with an error for inverted mesh elements. See Inverted Mesh Elements for more information. Sometimes, introducing extra boundaries with explicit deformation inside the domains can help. You can also generate a new mesh for the region covered by the deformed mesh and let the solver continue by deforming the new mesh; see the section Remeshing a Deformed Mesh. See also Tips for Modeling Using Deformed Meshes below.

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If you use a Geometry shape order larger than 1 in the Moving Mesh and Deformed Geometry interfaces, the mesh moving techniques often produce elements with distorted shapes. If there are warnings or errors about inverted mesh elements, consider reducing the geometry shape order to 1. This, however, makes the geometry representation polygonal, which might affect accuracy. The measure of mesh quality does not capture these distorted shapes because it is computed from the positions of the corners of the mesh element (ignoring midside nodes, for instance).