GitLab

- consistent with other blockEdge types
- adjust some debug output

- The arc will frequently enclose an angle less than 180 degrees.
  For the case, it is possible to define the arc by its endpoints
  and its centre (origin) point. For example,

      arc 0 1 origin (0 0 0);

  When defined in the way, any discrepancy in the arc radius for the
  endpoints is resolved by adjusting the origin to ensure that the
  average radius is satisfied.

  It is also possible to specify a \em flatness factor as a multiplier
  of the radius. For example,

      arc 0 1 origin 1.1 (0 0 0);

ENH: minor code cleanup for block edges

ENH: expose point appending as polyList::concat

- avoid potential ambiguities in naming of mesh faces/edges
  vs. block faces/edges

- additional methods characterizing the number of faces
  (internal, boundary, total) associated with a blockDescriptor

- cellLabel() accessor and checkIndex() methods

- restore demand-driven behaviour of block, cache the calculated cells
  and refactor generation of block boundary faces to improve potential
  reuse.

New functionality contributed by Mattijs Janssens:
  - new edge projection: projectCurve for use with new geometry
    'searchableCurve'
  - new tutorial 'pipe'
  - naming of vertices and blocks (see pipe tutorial). Including back
    substitution for error messages.

For example, to mesh a sphere with a single block the geometry is defined in the
blockMeshDict as a searchableSurface:

    geometry
    {
        sphere
        {
            type searchableSphere;
            centre (0 0 0);
            radius 1;
        }
    }

The vertices, block topology and curved edges are defined in the usual
way, for example

    v 0.5773502;
    mv -0.5773502;

    a 0.7071067;
    ma -0.7071067;

    vertices
    (
        ($mv $mv $mv)
        ( $v $mv $mv)
        ( $v  $v $mv)
        ($mv  $v $mv)
        ($mv $mv  $v)
        ( $v $mv  $v)
        ( $v  $v  $v)
        ($mv  $v  $v)
    );

    blocks
    (
        hex (0 1 2 3 4 5 6 7) (10 10 10) simpleGrading (1 1 1)
    );

    edges
    (
        arc 0 1 (0 $ma $ma)
        arc 2 3 (0 $a $ma)
        arc 6 7 (0 $a $a)
        arc 4 5 (0 $ma $a)

        arc 0 3 ($ma 0 $ma)
        arc 1 2 ($a 0 $ma)
        arc 5 6 ($a 0 $a)
        arc 4 7 ($ma 0 $a)

        arc 0 4 ($ma $ma 0)
        arc 1 5 ($a $ma 0)
        arc 2 6 ($a $a 0)
        arc 3 7 ($ma $a 0)
    );

which will produce a mesh in which the block edges conform to the sphere
but the faces of the block lie somewhere between the original cube and
the spherical surface which is a consequence of the edge-based
transfinite interpolation.

Now the projection of the block faces to the geometry specified above
can also be specified:

    faces
    (
        project (0 4 7 3) sphere
        project (2 6 5 1) sphere
        project (1 5 4 0) sphere
        project (3 7 6 2) sphere
        project (0 3 2 1) sphere
        project (4 5 6 7) sphere
    );

which produces a mesh that actually conforms to the sphere.

See OpenFOAM-dev/tutorials/mesh/blockMesh/sphere

This functionality is experimental and will undergo further development
and generalization in the future to support more complex surfaces,
feature edge specification and extraction etc.  Please get involved if
you would like to see blockMesh become a more flexible block-structured
mesher.

Henry G. Weller, CFD Direct.