The standard merge-algorithm is N^2 over the face-points and uses a
geometric proximity test for the merge. These are both choices for
implementation simplicity and are rather inefficient for large meshes.
I have now implemented an experimental linear topological merge
algorithm which is VERY fast and effective for meshes of any size.
Currently it will merge internal faces on meshes of arbitrary complexity
but does not yet handle edge or face collapse needed for wedges and
other degenerate blocks.
The new fast-merge algorithm may be selected using the optional
"fastMerge" entry:
fastMerge yes;
and if not present the standard N^2 algorithm will be used.
Henry G. Weller
CFD Direct
Consider a block describing a channel with two opposite walls.
Currently in order to grade the mesh towards the walls and have a
uniform region in the centre the channel would need to be spit into 3
blocks. With the new multi/sectional grading this can be achieved in a
single block e.g.
blocks
(
hex (0 1 2 3 4 5 6 7) (20 60 20)
simpleGrading
(
1
((0.2 0.3 4) (0.6 0.4 1) (0.2 0.3 0.25))
1
)
);
In this example the block is divided uniformly in the x and z -directions
and split into three grading sections in the y-direction described by
three triples: ((0.2 0.3 4) (0.6 0.4 1) (0.2 0.3 0.25)). Each of the
grading sections is described by a triple consisting of the fraction of
the block, the fraction of the divisions and the grading ratio (size of
first division/size of last division). Both the fraction of the block
and the fraction of the divisions are normalized automatically so they
can be specified scaled in anyway, e.g. as percentages:
blocks
(
hex (0 1 2 3 4 5 6 7) (20 60 20)
simpleGrading
(
1
((2 3 4) (6 4 1) (2 3 0.25))
1
)
);
and they need not sum to 1 or 100.
This is very new functionality and not well tested but backward
compatibility has been well tested so all existing blockMeshDicts should
parse correctly.
