+
+This hypothesis can be taken into account by
+\ref a1d_algos_anchor "Wire Discretization" and
+\ref a1d_algos_anchor "Composite Side Discretization" algorithms.
+
+<b>See Also</b> a sample TUI Script of a
+\ref tui_propagation "Propagation hypothesis" operation
+
+\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 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 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.
+
+<br><b>See also</b> a sample TUI script of a \ref tui_viscous_layers
+"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>