Rather than requiring each functionObject to handle failed construction
internally (using the active_ flag) the static member function "viable"
is provided which returns true if construction of the functionObject is
likely to be successful. Failed construction is then handled by the
wrapper-class which constructs the functionObject,
e.g. "OutputFilterFunctionObject".
Previous behavior which may be useful for moving-mesh cases can be
selected using the optional entry:
writeTotalArea yes;
The initial total area is written in the log and data file header e.g.:
# Source : faceZone f0
# Faces : 8
# Area : 1.063860e-02
