Adaptive Mesh Refinement (Stationary and Eigenvalue Adaptation)

The node (

) is a solver attribute that handles adaptive mesh refinement together with a Stationary Solver or Eigenvalue Solver. For information about the time-dependent node, see Adaptive Mesh Refinement (Time-Dependent Adaptation) below.

	For stationary and eigenvalue solvers, the Adaptive Mesh Refinement node cannot be added manually but is instead added by the solvers to indicate that they run an adaptive mesh refinement. The Adaptive Mesh Refinement node then only includes an Output section with information about the adaptation solutions and meshes.

The list shows the study step from which the main settings for adaptive mesh refinement are taken. Depending on the settings in the study step, some settings below are not available because they are specified in the study step’s settings. Choose to define all adaptive mesh refinement setting here.

Use the list to specify that geometry. If you have specified the geometry in the stationary or eigenvalue study step, which appears in the list above, this list is not available.

From the list, select which solution that should be used to evaluate error estimates:

In the field (only available when is or ), enter weights as a space-separated list of positive (relative) weights so that the error estimate is a weighted sum of the error estimates for the various solutions (eigenmodes). The default value is 1, which means that the weight is put on all solutions (eigenmodes). If the number of weights is larger than 1 but less than the number of solutions, the omitted weights are treated as zero weights.

The check box is selected per default. Clear this check box if you do not want to save solution on every adapted mesh. In that case, the last two solutions are saved (the finest one and the second finest) regardless of the total number of solutions.

Under , the following settings are available.

Use the list to control how to adaptively refine mesh elements. Select one of these methods:

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, to use the current mesh as a starting point and modify it by refinements, coarsening, topology modification, and point smoothing. Use the check box to control if mesh coarsening is used. If the mesh contains anisotropic elements (for example, a boundary layer mesh), it is best to disable mesh coarsening to preserve the anisotropic structure. If you have selected to allow coarsening, specify the (a value of 5 by default) to scale the refined mesh size in the regions where refinement is not needed.

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, to set up a size expression describing the error and rebuild the meshing sequence using the size expression as input. Note that structured meshes, such as mapped and swept meshes, in general are not appropriately refined. This method is not supported on imported meshes. The size of the refined mesh is the minimum of the size of the original mesh (previous refined mesh) and the size defined by the refinement. Specify the (a value of 3 by default) to scale the refined mesh size in the regions where refinement is not needed.

•

, to make the solver refine elements in a regular pattern by bisecting all edges of an element that needs refinement.

•

, to make the solver refine only the longest edge of an element by recursively bisecting the longest edge of edge elements that need refinement. This method is less suitable for models with nonsimplex elements. This is the default method.

For all adaptation methods except , you can specify the maximum number of refinements of the mesh elements (default: 5) in the field.

Use the list to specify how the solver should select which elements to refine. Select:

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to minimize the error by refining a fraction of the elements with the largest error in such a way that the total number of elements increases roughly by the factor specified in the accompanying field. The default value is 1.7, which means that number of elements increases by about 70%.

•

to refine elements whose local error indicator is larger than a given fraction of the largest local error indicator. Use the accompanying field to specify the fraction. The default value is 0.5, which means that the fraction contains the elements with more than 50% of the largest local error.

•

to refine a given fraction of the elements. Use the accompanying field to specify the fraction. The default value is 0.5, which means that the solver refines about 50% of the elements.

Use the field to specify the maximum number of elements in the refined mesh. If the number of elements exceeds this number, the solver stops even if it has not reached the number specified in the field. The default value is 10,000,000 (ten million) elements.

With the set to or , you can control the display of convergence from the adaptation when the check box is selected. It is possible to choose the plot window to display the convergence as well as the table to be used by the plot from the — select (the default) or — and lists, respectively. If you choose from the list, two new tables are created, one for the adaptation convergence plot and one for providing verbose information.

Also choose the level of detail for the log from the list: , (the default), or . Choose if you want to include the evaluations for all the parameters, frequencies, or eigenvalues in the log.

Use the field to specify the maximum number of adaptive mesh refinement iterations. The default value is 5 in 1D, 2 in 2D, and 1 in 3D. With the set to , the default value is set to 20 in 1D, 15 in 2D, and 10 in 3D.

In this section you find information about the adaptation solutions and meshes, with the tags for the and nodes for each level in the adaptive mesh refinement.

If desired, select the check box to use the adaptive method from versions 6.0 and earlier, in which higher-order names of DOFs for vector elements are ignored in the residual calculation.