In this branch, the general aspects for meshing are considered. The parameters set here are taking into account for all the available meshers inside GiD.
GiD can work with three main mesh types:
- Body-fitted: This mesh type corresponds to a body-fitted Finite Elements-like mesh. The mesh is fitted to the contours of the geometrical entities.
- Embedded: This mesh type corresponds to an embedded mesh (not fitted to the contours of the embedded closed region). This kind of models have one or more geometrical volumes (the calculation volumes) and an embedded closed region. The calculation volumes are meshed in a body-fitted way, and its nodes have the extra information of (signed) distance to the contours of the embedded region. Positive distance indicates the node is outside the embedded contour. The definition of the embedded closed region is done by geometrical surfaces, and it is not needed for them to be watertight, considering as acceptable small gaps and overlapping entities in its definition.
All the geometrical volumes in the model are considered calculation volumes, and all the surfaces not belonging to any volume (surfaces with higherentity 1) are considered as contours of the embedded region.
The scalar field of distances of the calculation nodes to the embeeded boundary could be asked programatically with the GiD-Tcl scripting command "GiD_Info Mesh EmbeddedDistances". See Customization manual for its syntax. This information could be of interest to be written in the calculation file input of the simulation.
When changing to postprocess a result named "Distance" will be automatically created (in the first time step of an analysis named "Signed distance"). This result is interesting to visualice the field of distances, and to create the iso-surface of distance=0.0 to see how is represented the boundary for the embedded simulation.
If embedded mesh is selected, user can choose to get the elements with all its nodes out of the embedded closes region or not (in order to save memory and make faster the calculation process of the solver). This option is located in the Meshing->Other branch of preferences window.
- Cartesian: This mesh type corresponds to a Finite Differences-like mesh, a cartesian grid aligned to XYZ axes. Specific options for this mesh type can be found in Cartesian.
It has to be noted that working with a model in GiD, the whole model is treated as the selected mesh type.
Some of the options in preferences window may appear or hide depending ont the mesh type chosen.
Default quadratic type
This property set the default quadratic type of the elements to be generated. User can choose between three options:
- Linear: linear elements are made.
- Quadratic: the elements will be quadratic, with a node in the middle of each edge:
Linear: 3 nodes.
Triangle: 6 nodes.
Quadrilateral: 8 nodes.
Tetrahedra: 10 nodes.
Hexahedra: 20 nodes.
Prisms: 15 nodes.
- Quadratic9: option is similar to Quadratic, but will generate 9-noded quadrilaterals and 27-noded hexahedra (an extra node in the middle of the element, and in the middle of the element faces for hexahedra case).
The different conectivities can be seen at Element type.
This variable set the default quadratic type (used the first time a mesh is generated in a model). It does not modify the quadratic type of a model previously meshed. To set the mesh quadratic type of a model go to (Quadratic type).
Automatic correct sizes
This preference lets GiD make an automatic mesh size correction just before meshing begins, in order to compatibilize mesh sizes assigned to close geometrical entities.
There are three possible options:
- None: if None is set, no size correction is made.
- Normal: if Normal is set, a size correction is made according to the sizes of geometrical entities and the compatibility between meshing sizes of neighboring entities.
- Hard: if Hard is set, the Normal correction is made and, furthermore, an automatic chordal error criteria is applied to assign sizes to surfaces which are the contours of some volume, so as to improve the probability of success of the unstructured volume mesher.
Unstructured size transitions
- This parameter controls whether the transitions between different element sizes are slow or fast. In models with different mesh sizes assigned, a low value of this parameter will imply meshes with more elements than using a high value.
- Regular transition near boundary: This preference is used to control the transition of sizes pattern. If this preference is set, the transition size follows in a more parallel way the elements in the boundary of the mesh; otherwise (if the preference is not set) the size transition is more uniform along the mesh.