Tips for Modeling Using Deformed Meshes

When working with a deformed mesh to move things around, the computational mesh gets deformed. If the deformations become too large, some mesh elements might get inverted. This means that the accuracy of the solution deteriorates and eventually the solvers diverge due to an ill-conditioned system. Here are some tips on how to keep the mesh under control:

•	Try a different mesh. It is often preferable to start from a reasonably uniform mesh. One way to achieve this is to first select a coarse mesh in the predefined mesh size settings and then set a small maximum element size. Also, quad meshes and mapped meshes tend to perform better than triangles.

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Try a different smoothing type. Winslow smoothing is slightly slower, more memory consuming, and usually, but not always, more stable than Laplace smoothing. Hyperelastic and Yeoh smoothing sometimes work better than the other methods (in some fluid-structure interaction problems, for example). See Smoothing Methods for more information.

•	If solving a time-dependent problem, try to solve the equations more accurately by reducing the absolute and relative tolerances for the time-dependent solver.

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Help the mesh deformation by sliding the boundary elements along with the movement of the mesh. This can be achieved by adding a prescribed deformation on the boundary that moves the boundary elements according to the deformation of some point in the model. Define a coupling operator under the Definitions node and use it to couple the deformation from the point to the boundary mesh.

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Physics interfaces that control the coordinates of one of the frames exhibit an override behavior where a physics interface of this kind further down the list of physics interfaces in the model tree overrides the ones above, if they are active on the same domains. The Moving Mesh interface appears as not applicable where it is overridden, but physics interfaces with ALE functionality, such as the Solid Mechanics interface, only loose their control over the frame. You may need to rearrange the order of the physics interfaces in a model to avoid this behavior.