smesh/doc/salome/gui/SMESH/input/additional_hypo.doc

/*!

\page additional_hypo_page Additional Hypotheses

\n <b>Additional Hypotheses</b> can be applied as a supplement to the
main hypotheses, introducing additional concepts to mesh creation.

To define an <b>Additional Hypothesis</b> simply select it in
<b>Create Mesh</b> menu. These hypotheses are actually changes in the
rules of mesh creation and as such don't possess adjustable values.

\anchor non_conform_allowed_anchor
<h2>Non Conform mesh allowed hypothesis</h2>

<b>Non Conform mesh allowed</b> hypothesis allows to generate non-conform
meshes (that is, meshes having some edges ending on an edge or face of
adjacent elements).

\anchor quadratic_mesh_anchor
<h2>Quadratic Mesh</h2>

Quadratic Mesh hypothesis allows to build a quadratic mesh (whose
edges are not straight but curved lines and can be defined by three
points: first, middle and last instead of an ordinary two).

See \ref adding_quadratic_elements_page
for more information about quadratic meshes.

\anchor propagation_anchor
<h2>Propagation of 1D Hypothesis on opposite edges</h2>

<b>Propagation of 1D Hypothesis on opposite edges</b> allows to propagate a
hypothesis 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 hypothesis, unless another hypothesis
has been locally defined on the opposite edge.
 
<br><b>See Also</b> a sample TUI Script of a 
\ref tui_propagation "Propagation hypothesis" operation

\anchor propagofdistribution_anchor
<h2>Propagation of Node Distribution on Opposite Edges</h2>

<b>Propagation of Node Distribution on Opposite Edges</b> 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.
 
<br><b>See Also</b> a sample TUI Script of a 
\ref tui_propagation "Propagation hypothesis" operation

\anchor quadrangle_preference_anchor
<h2>Quadrangle Preference</h2>

This additional hypothesis can be used together with 2D triangulation algorithms.
It allows 2D triangulation algorithms to build quadrangular meshes.

When used with "Quadrangle (Mapping)" meshing algorithm, that is obsolete
 since introducing \ref hypo_quad_params_anchor "Quadrangle parameters" 
hypothesis, this hypothesis has one restriction on its work: the total quantity of 
segments on all four sides of the face must be even (divisible by 2).

\anchor viscous_layers_anchor
<h2>Viscous Layers and Viscous Layers 2D</h2>

<b>Viscous Layers</b> and <b>Viscous Layers 2D </b> additional
hypotheses can be used together with either some 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 html viscous_layers_hyp.png

<ul>
<li><b>Name</b> - allows to define the name of the hypothesis.</li>
<li><b>Total thickness</b> - gives the total thickness of element layers.</li>
<li><b>Number of layers</b> - defines the number of element layers.</li>
<li><b>Stretch factor</b> - defines the growth factor of element height
  from the mesh boundary inwards.</li>
<li><b>Specified Faces/Edges are</b> - defines how the shapes specified by
  the next parameter are used.
<li><b> Faces/Edges with/without layers</b> - 
  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 (<b>Specified Faces/Edges are</b>). 
  Faces (or edges) can be selected either in the Object Browser or in
  the VTK Viewer.
  \note A mesh shown in the 3D Viewer can prevent selection of faces
  and edges, just hide the mesh to avoid this. 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 "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.
  \image html viscous_layers_on_submesh.png 2D viscous layers constructed on boundary edges of a sub-mesh on a disk face.

  If you use \b 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. <br>
  Also you can't define different number of layers on adjacent faces
  of a solid.<br>
  This logic is also valid for the 2D hypothesis.
</li>
</ul>

\image html viscous_layers_mesh.png A group containing viscous layer prisms.

<br><b>See also</b> a sample TUI script of a \ref tui_viscous_layers
"Viscous layers construction".

*/