`**adaptation`#

Description#

This command is used to remesh and/or optimize a Zebulon mesh (2D, 3D or surfacic) by means of external remeshing libraries. It’s main focus is on defining options for preserving FEM entities in order to repeat a computation on the new mesh. Any external remesher should be able to preserve these entities. Additional specific instructions may be required.

Syntax#

The command has the following syntax:

**adaptation \(~\,\) *min_size hmin \(~\,\) *max_size hmax \(~\,\) [ *surface_mesher surface-mesher ] \(~\,\) [ *volume_mesher 2d-or-3d-mesher ] \(~\,\) *metric [ default/scalar/from_function/from_file/uniform_from_field/ ] \(~\,\) [ *verbose int-value ] \(~\,\) [ *preserve_elsets elsets-names ] \(~\,\) [ *preserve_elsets_start_with elsets-start-with-names ] \(~\,\) [ *preserve_bsets bsets-names ] \(~\,\) [ *preserve_bsets_start_with bsets-start-with-names ] \(~\,\) [ *freeze_elsets elsets-names ] \(~\,\) [ *freeze_elsets_start_with elsets-start-with-names ] \(~\,\) [ *freeze_bsets bsets-names ] \(~\,\) [ *freeze_bsets_start_with bsets-start-with-names ] \(~\,\) [ *freeze_nsets nsets-names ] \(~\,\) [ *freeze_nsets_start_with nsets-start-with-names ] \(~\,\) [ *freeze_fasets_geom fasets-names ] \(~\,\) [ *freeze_fasets_geom_start_with fasets-start-with-names ] \(~\,\) [ *ridges lisets-names ] \(~\,\) [ *ridges_start_with lisets-start-with-names ] \(~\,\) [ *corners nsets-names ] \(~\,\) [ *corners_start_with nsets-start-with-names ]

*min_size: imposes minimal edge size.
*max_size: imposes maximal edge size.
*surface_mesher: sets the 3D surface remesher. For now, only the option mms is available. Note that, some of the following options don’t apply to this kind of remesher.
*volume_mesher: sets the volume remesher. For now, only the option mmg3d is available for a 3D mesh and mmg2d for a 2D mesh. Note that, all options are automatically transferred from adaptation to the remesher.
*metric default: creates the size map of the current mesh defined by the mean edge lenghts of the mesh. It has the following syntax :

*metric default [factor double-val ] [min_size double-val] [max_size double-val ] [output_file ascii-file-name ]

where min_size and max_size are usually taken equal to the previous ones from adaptation, but can also be different. The factor is a multiplication factor of the default metric.

*metric scalar: imposes a constant isotropic metric. It has the following syntax :

*metric scalar \(~\,\) value double-val \(~\,\) [ min_size double-val ] \(~\,\) [ max_size double-val ] \(~\,\) [ output_file ascii-file-name ]
*metric from_function: creates a size map using the nodes coordinates which satisfy the given function. Remember to include a semicolon at the end of the function definition. The complete syntax is the following one :

*metric from_function \(~\,\) func function; \(~\,\) [ min_size double-val ] \(~\,\) [ max_size double-val ] \(~\,\) [ output_file ascii-file-name ]
*metric from_file: reads a nodal size map from a file. The syntax is:

*metric from_file \(~\,\) file file-name \(~\,\) [ min_size double-val ] \(~\,\) [ max_size double-val ] \(~\,\) [ output_file ascii-file-name ]

where file-name defines the name of an ASCII file containing the prescribed size map for the new mesh. The ASCII file should contain the following lines:

first line

\(n_b\) (number of the initial mesh points : 1 integer)
line 2 to \(n_b +1\)

\(x_i\), \(y_i\), \(z_i\), \(d_i\) (definition of \(P_i\) coordinates and prescribes size : 4 double values).

Note that, if the number of prescribed sizes is different of the number of the mesh nodes, a transfer through the closest neighbour method is done.

*metric: uniform_from_field creates a size map based on a uniform distribution of a given field (usually the discretization error estimate) for a target value of accuracy. The syntax is :

*metric uniform_from_field \(~\,\) field \(\eta\) \(~\,\) accuracy \(\tau\) \(~\,\) [ min_size double-val ] \(~\,\) [ max_size double-val ] \(~\,\) [ output_file ascii-file-name ]

The new size map is computed by the formula

(1)#\[h_{new,\Omega_E} = h_{old,\Omega_E} \frac{\tau^\frac{1}{p}}{\eta_{\Omega_E}^\frac{2}{2p+d}(\sum_{\Omega_E}\eta_{\Omega_E}^\frac{2d}{2p+d})^\frac{1}{2p}}\]

where \(d\) is the dimension, \(p\) the finite elements interpolation degree and \(h_{old}\) the default metric of the initial mesh. Note that, this metric can only be used during an adaptive procedure or when an initial solution exists, as the field \(\eta\) is either read from a solution file or computed by a previous computational step.

*verbose: prints detailed information aboutthe remeshing process. Takes integer values between 0 and 6. The default value is 1.
*preserve_elsets (preserve_elsets_start_with): preserves the given element sets. Set surface interpolation and nodes insertion are allowed.
*preserve_bsets (preserve_bsets_start_with): preserves the given boundary (liset/faset) sets. Interpolation and nodes insertion are allowed.
*freeze_elsets (freeze_elsets_start_with): freezes the given element sets. Surface interpolation and nodes insertion are forbidden.
*freeze_bsets (freeze_bsets_start_with): freezes the given boundary (liset/faset) sets. Interpolation and nodes insertion are forbidden.
*freeze_nsets (freeze_nsets_start_with): freezes the given node sets. The new mesh will contain the initial nodes, at their exact initial positions, and, for parallel purpose, their initial ranks. Note that, nodes insertion is allowed. Thus, for use in a boundary condition please transform the nset in bset and use the freeze_bset option.
*freeze_fasets_geom (freeze_fasets_geom_start_with): freezes the geometry of a surface (faset). Interpolation is forbidden, but nodes insertion is allowed.
*ridges (ridges_start_with): preserves line sets (lisets). We define a ridge as a curvature line (liset) which locally splits a surface in two smooth surfaces. In the geometry optimization step, this line imposes an independent optimization on each one of its sides. It can be seen as a CAO information to be preserved.
*corners (corners_start_with): preserves node sets. It is similar to a ridge, but on nodes. The geometry of each surface splitted by a corner is set to be independently optimized.

Example#

****mesher
 ***mesh
  **open hole_toy
  **adaptation
   *min_size .001
   *max_size 2.
   *verbose   6
   *metric scalar
    value 0.15
   *volume_mesher mmg3d
    hgrad 1.25
    hausd 0.005
   *freeze_elsets eset_overlap
   *preserve_elsets_start_with eset
   *freeze_bsets left
   *preserve_bsets right front
   *corners_start_with corn
  **output adaptation_hole_toy_remeshed.geof
****return

****mesher
 ***mesh
  **open carre.geof
  **adaptation
   *metric scalar
    value 0.1
   *min_size .1
   *max_size 2.
   *volume_mesher mmg2d
    hgrad 1.
   *verbose 6
   *preserve_elsets diag mix
   *freeze_elsets diag
   *preserve_bsets  left top bottom
   *freeze_nsets diag
  **output carre_remeshed.geof
****return

**adaptation

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**adaptation#

Description#

Syntax#

Example#

`**adaptation`#