The mapFields utility maps one or more fields relating to a given geometry
onto the corresponding fields for another geometry. It is completely generalised in
so much as there does not need to be any similarity between the geometries to
which the fields relate. However, for cases where the geometries are consistent,
mapFields can be executed with a special option that simplifies the mapping
process.
For our discussion of mapFields we need to define a few terms. First, we say
that the data is mapped from the source to the target. The fields are deemed
consistent if the geometry and boundary types, or conditions, of both source and
target fields are identical. The field data that mapFields maps are those fields
within the time directory specified by startFrom/startTime in the controlDict of
the target case. The data is read from the equivalent time directory of the
source case and mapped onto the equivalent time directory of the target
case.
When the fields are not consistent, as shown in 5.18, mapFields requires a
mapFieldsDict dictionary in the system directory of the target case. The following
rules apply to the mapping:
the field data is mapped from source to target wherever possible,
i.e. in our example all the field data within the target geometry is
mapped from the source, except those in the shaded region which
remain unaltered;
the patch field data is left unaltered unless specified otherwise in the
mapFieldsDict dictionary.
The mapFieldsDict dictionary contain two lists that specify mapping of patch data.
The first list is patchMap that specifies mapping of data between pairs of source
and target patches that are geometrically coincident, as shown in 5.18. The list
contains each pair of names of source and target patch. The second list is
cuttingPatches that contains names of target patches whose values are to be
mapped from the source internal field through which the target patch cuts. In the
situation where the target patch only cuts through part of the source
internal field, e.g. bottom left target patch in our example, those values
within the internal field are mapped and those outside remain unchanged.
Figure 5.18:
Mapping inconsistent fields
An example mapFieldsDict dictionary is shown below:
