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

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\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 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When used with "Quadrangle (Mapping)" meshing algorithm, that is obsolete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 Edges are</b> - defines how the shapes specified by
  the next parameter are used.
<li><b>Faces without layers</b> and <b>Edges with/without layers</b> - 
  in the 3D case it defines geometrical faces on which element layers
  should not be constructed; in the 2D case it defines geometrical edges
  on which element layers either should be or should not be
  constructed, depending on the value of the previous parameter
  (<b>Specified Edges are</b>). Whatever shapes are specified by this
  parameter, 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.
  \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).
</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".


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