\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.
+An <b>Additional Hypothesis</b> can be defined in the same way as any
+main hypothesis in \ref create_mesh_anchor "Create Mesh" or
+\ref constructing_submeshes_page "Create Sub-Mesh" dialog.
+
+The following additional hypothesis are available:
+<ul>
+<li>\ref propagation_anchor "Propagation of 1D Hypothesis on opposite edges"
+ and \ref propagofdistribution_anchor "Propagation of Node Distribution on Opposite Edges"
+ hypotheses are useful for creation of quadrangle and hexahedral
+ meshes.</li>
+<li>\ref viscous_layers_anchor "Viscous Layers" and
+ \ref viscous_layers_anchor "Viscous Layers 2D"
+ hypotheses allow creation of layers of highly stretched
+ elements near mesh boundary, which is beneficial for high quality
+ viscous computations.</li>
+<li>\ref quadratic_mesh_anchor "Quadratic Mesh" hypothesis allows
+ generation of second order meshes.</li>
+<li>\ref quadrangle_preference_anchor "Quadrangle Preference"
+ enables generation of quadrangles.</li>
+</ul>
-\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 propagation_anchor
+<h2>Propagation of 1D Hypothesis on opposite edges</h2>
-\anchor quadratic_mesh_anchor
-<h2>Quadratic Mesh</h2>
+<b>Propagation of 1D Hypothesis on opposite edges</b> allows to mesh
+opposite sides of a quadrangle face and other adjacent quadrangles,
+using the same hypothesis assigned to only one edge.<br>
+Thus you define a sub-mesh on the edge where you define 1D meshing
+parameters and the \b 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.
-Quadratic Mesh hypothesis allows to build a quadratic mesh (whose
-edges are not straight but broken lines and can be defined by three
-points: first, middle and last) instead of an ordinary one.
+This hypothesis can be taken into account by
+\ref a1d_algos_anchor "Wire Discretization" and
+\ref a1d_algos_anchor "Composite Side Discretization" algorithms.
-\anchor propagation_anchor
-<h2>Propagation of 1D Hypothesis on opposite edges</h2>
+<b>See Also</b> a sample TUI Script of a
+\ref tui_propagation "Propagation hypothesis" operation
-<b>Propagation of 1D Hypothesis on opposite edges</b> allows to propagate a
-hypothesis onto an opposite edge. If a local hypothesis and
+\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 hypothesis, unless another hypothesis
+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.
+This hypothesis can be taken into account by
+\ref a1d_algos_anchor "Wire Discretization" and
+\ref a1d_algos_anchor "Composite Side Discretization" algorithms.
-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).
+<b>See Also</b> a sample TUI Script of a
+\ref tui_propagation "Propagation hypothesis" operation
\anchor viscous_layers_anchor
-<h2>Viscous Layers</h2>
-
-<b>Viscous Layers</b> additional hypothesis can be used together with
-some 3D algorithms, Hexahedron(i,j,k) for example. This
-hypothesis allows creation of layers of highly stretched prisms near
-mesh boundary, which is beneficial for high quality viscous
-computations. The prisms constructed on the quadrangular mesh faces are
-actually the hexahedrons.
+<h2>Viscous Layers and Viscous Layers 2D</h2>
+<b>Viscous Layers</b> and <b>Viscous Layers 2D </b> 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 html viscous_layers_hyp.png
+\image html viscous_layers_2d_hyp.png
+
<ul>
<li><b>Name</b> - allows to define the name of the hypothesis.</li>
-<li><b>Total thicknes</b> - gives the total thickness of prism layers.</li>
-<li><b>Number of layers</b> - defines the number of prism layers.</li>
-<li><b>Stretch factor</b> - defines the growth factor of prism height
-from the mesh boundary inwards.</li>
-<li><b>Faces without layers</b> - defines geometrical faces on which
-prism layers should not be constructed. By default the prism layers
-are not constructed on geometrical faces shared by solids.</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>Extrusion method</b> (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.
+<ul><li><b>Surface offset + smooth</b> 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.</li>
+ <li><b>Face offset</b> 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.</li>
+ <li><b>Node offset</b> 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.</li>
+\image html viscous_layers_extrusion_method.png "Prisms created by the tree extrusion methods at the same other parameters"
+</ul></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. \b 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.<br>
+ 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.
"Viscous layers construction".
+\anchor quadratic_mesh_anchor
+<h2>Quadratic Mesh</h2>
+
+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 a1d_algos_anchor "Wire Discretization" and
+\ref a1d_algos_anchor "Composite Side Discretization" algorithms. To
+create a quadratic mesh assign this hypothesis at
+\ref constructing_meshes_page "mesh construction".
+
+See \ref adding_quadratic_elements_page
+for more information about quadratic meshes.
+
+
+\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.
+
+Usage of this hypothesis with "Quadrangle (Mapping)" meshing algorithm
+is obsolete since introducing
+\ref hypo_quad_params_anchor "Quadrangle parameters" hypothesis.
+Usage of this hypothesis with "Quadrangle (Mapping)" meshing algorithm
+corresponds to specifying "Quadrangle Preference" transition type of
+\ref hypo_quad_params_anchor "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.
*/
