X-Git-Url: http://git.salome-platform.org/gitweb/?p=modules%2Fsmesh.git;a=blobdiff_plain;f=doc%2Fgui%2Finput%2Fadditional_hypo.rst;fp=doc%2Fgui%2Finput%2Fadditional_hypo.rst;h=6fa98f9c29687becdc4a6b4da847f2e9299285af;hp=0000000000000000000000000000000000000000;hb=4cf07a14111e98e8889620ee7e6371574c31a50c;hpb=d9f4b53e489dd5857db264ede6acded7b076c9f1 diff --git a/doc/gui/input/additional_hypo.rst b/doc/gui/input/additional_hypo.rst new file mode 100644 index 000000000..6fa98f9c2 --- /dev/null +++ b/doc/gui/input/additional_hypo.rst @@ -0,0 +1,169 @@ +.. _additional_hypo_page: + +********************* +Additional Hypotheses +********************* + +**Additional Hypotheses** can be applied as a supplement to the main hypotheses, introducing additional concepts to mesh creation. + +An **Additional Hypothesis** can be defined in the same way as any main hypothesis in :ref:`Create Mesh ` or :ref:`Create Sub-Mesh ` dialog. + +The following additional hypothesis are available: + +* :ref:`propagation_anchor` and :ref:`propagofdistribution_anchor` hypotheses are useful for creation of quadrangle and hexahedral meshes. +* :ref:`Viscous Layers ` and :ref:`Viscous Layers 2D ` hypotheses allow creation of layers of highly stretched elements near mesh boundary, which is beneficial for high quality viscous computations. +* :ref:`quadratic_mesh_anchor` hypothesis allows generation of second order meshes. +* :ref:`quadrangle_preference_anchor` hypothesis enables generation of quadrangles. + + + +.. _propagation_anchor: + +Propagation of 1D Hypothesis on opposite edges +############################################## + +**Propagation of 1D Hypothesis on opposite edges** allows to mesh +opposite sides of a quadrangle face and other adjacent quadrangles, +using the same hypothesis assigned to only one edge. +Thus you define a sub-mesh on the edge where you define 1D meshing +parameters and the **Propagation hypothesis**. These local meshing +parameters will be propagated via opposite sides of quadrangles to the +whole geometry, and this propagation stops at an edge with other local +meshing parameters. + +This hypothesis can be taken into account by +:ref:`Wire Discretization ` and +:ref:`Composite Side Discretization ` algorithms. + +**See Also** a sample TUI Script of a :ref:`Propagation hypothesis ` operation + +.. _propagofdistribution_anchor: + +Propagation of Node Distribution on Opposite Edges +################################################## + +**Propagation of Node Distribution on Opposite Edges** allows to propagate +distribution of nodes onto an opposite edge. If a local hypothesis and +propagation are defined on an edge of a quadrangular face, the +opposite edge will have the same number of nodes and the same +relations between segment lengths, unless another hypothesis +has been locally defined on the opposite edge. + +This hypothesis can be taken into account by +:ref:`Wire Discretization ` and +:ref:`Composite Side Discretization ` algorithms. + +**See Also** a sample TUI Script of a :ref:`Propagation hypothesis ` operation + +.. _viscous_layers_anchor: + +Viscous Layers and Viscous Layers 2D +#################################### + +**Viscous Layers** and **Viscous Layers 2D** additional +hypotheses can be used by several 3D algorithms, for example +Hexahedron(i,j,k), or 2D algorithms, for example Triangle +(MEFISTO), correspondingly. These hypotheses allow creation of layers +of highly stretched elements, prisms in 3D and quadrilaterals in 2D, +near mesh boundary, which is beneficial for high quality viscous +computations. + +.. image:: ../images/viscous_layers_hyp.png + :align: center + +.. image:: ../images/viscous_layers_2d_hyp.png + :align: center + + +* **Name** - allows to define the name of the hypothesis. +* **Total thickness** - gives the total thickness of element layers. +* **Number of layers** - defines the number of element layers. +* **Stretch factor** - defines the growth factor of element height from the mesh boundary inwards. +* **Extrusion method** (available in 3D only) - defines how positions of nodes are found during prism construction and how the creation of distorted and intersecting prisms is prevented. + + * **Surface offset + smooth** method extrudes nodes along the normal to the underlying geometrical surface. Smoothing of the internal surface of element layers is possible to avoid creation of invalid prisms. + * **Face offset** method extrudes nodes along the average normal of surrounding mesh faces to the intersection with a neighbor mesh face translated along its own normal by the thickness of layers. The thickness of layers can be limited to avoid creation of invalid prisms. + * **Node offset** method extrudes nodes along the average normal of surrounding mesh faces by the thickness of layers. The thickness of layers can be limited to avoid creation of invalid prisms. + + .. image:: ../images/viscous_layers_extrusion_method.png + :align: center + + .. centered:: + Prisms created by the tree extrusion methods at the same other parameters + +* **Specified Faces/Edges are** - defines how the shapes specified by the next parameter are used. +* **Faces/Edges with/without layers** - defines geometrical faces or edges on which element layers either should be or should not be constructed, depending on the value of the previous parameter (**Specified Faces/Edges are**). Faces (or edges) can be selected either in the Object Browser or in the VTK Viewer. **Add** button becomes active as soon as a suitable sub-shape is selected. + + .. note:: + A mesh shown in the 3D Viewer can prevent selection of faces and edges, just hide the mesh to avoid this. If a face, which should be selected, is hidden by other faces, consider creating a group of faces to be selected in the Geometry module. To avoid a long wait when a geometry with many faces (or edges) is displayed, the number of faces (edges) shown at a time is limited by the value of :ref:`Sub-shapes preview chunk size ` preference (in Preferences/Mesh/General tab). + + + If faces/edges without layers are specified, the element layers are + not constructed on geometrical faces shared by several solids in 3D + case and edges shared by several faces in 2D case. In other words, + in this mode the element layers can be constructed on boundary faces + and edges only, and are not constructed on internal faces and + edges. There is an exception to this rule: if a hypothesis is + assigned to a sub-mesh, the element layers can be constructed on + boundary faces/edges of the shape of this sub-mesh, at same time + possibly being internal faces/edges within the whole model. + +* **Create groups from layers** - activates creation of a group containing elements of the layers. + + .. image:: ../images/viscous_layers_on_submesh.png + :align: center + + .. centered:: + 2D viscous layers constructed on boundary edges of a sub-mesh on a disk face. + + If you use **several** hypotheses to define viscous layers on faces of + one solid, keep in mind the following. Each hypothesis defines a set + of faces with viscous layers (even if you specify faces without + layers). The sets of faces with viscous layers defined by several + hypotheses should not intersect, else the module won't add an + hypothesis that is incompatible with another one. + Also you can't define different number of layers on adjacent faces + of a solid. + This logic is also valid for the 2D hypothesis. + + + +.. image:: ../images/viscous_layers_mesh.png + :align: center + +.. centered:: + A group containing viscous layer prisms. + +**See also** a sample TUI script of a :ref:`tui_viscous_layers`. + + +.. _quadratic_mesh_anchor: + +Quadratic Mesh +############## + +Quadratic Mesh hypothesis allows to build a quadratic mesh (in which +links between element nodes are not straight but curved lines due to +presence of an additional mid-side node). + +This 1D hypothesis can be taken into account by +:ref:`Wire Discretization ` and +:ref:`Composite Side Discretization ` algorithms. To create a quadratic mes assign this hypothesis at +:ref:`mesh construction `. + +See :ref:`adding_quadratic_elements_page` for more information about quadratic meshes. + + +.. _quadrangle_preference_anchor: + +Quadrangle Preference +##################### + +This additional hypothesis can be used together with 2D triangulation algorithms. +It allows 2D triangulation algorithms to build quadrangular meshes. + +Usage of this hypothesis with :ref:`Quadrangle: Mapping ` meshing algorithm is obsolete since introducing :ref:`Quadrangle parameters ` hypothesis. +Usage of this hypothesis with :ref:`Quadrangle: Mapping ` meshing algorithm corresponds to specifying *Quadrangle Preference* transition type of :ref:`Quadrangle parameters ` hypothesis. + +.. note:: + *Quadrangle Preference* transition type can be used only if the total quantity of segments on all sides of the face is even (divisible by 2), else *Standard* transition type is used.