FLUENT - Workaround for pathline plots with unacceptable color distribution (insufficient number of colors to represent all pathlines tracked)
If you create a pathline plot and use Particle ID as the "Color By" variable, you may get an unacceptable distribution of colors, particularly if you are releasing the particles from zone faces or surfaces created with the Surface tools. There may be multiple pathlines with the same color.
The problem is a result of the fact that in FLUENT, the range of Particle ID is automatically (and arbitrarily) set to 30. Thus, if you have more than 30 facets, say, on a zone surface, and thus have more than 30 particles being released, all particle ids greater than 30 will be colored red! The workaround is simple:
(1) Access Surface->Manage, click on the zone or surface and note the number of facets.
(2) Deselect "Autorange" in Display->Pathlines and use the number of facets as the max value for Particle ID
(3) Plot the pathlines as usual