How can the default number of circumferential stage interface bands be changed?
There is an undocumented expert parameter:
ggi stage groups max = 40
40 is the default.
Q: How does the algorithm work, that forms the stage interface bands?
A: The control by the expert parameter "ggi stage groups max = 40" determines the "minimum size" for any given band. So if it is set to 1000, for example, then the smallest spanwise band will be no less than 1/1000 of the span. Many bands will be larger than this, as the local mesh dictates, especially in the middle span region.
Setting the expert parameter to some large number will create fine stage bands where the mesh is very fine in the boundary layer region, and then larger/thicker bands away from there where the mesh is coarser.