Checking mapping is important and Nastran offers this possibility by writing a specific file that can be then read by Patran displaying the picture below.
To get this mapping file, this is an option that is accessible inside CosimPrePlus
Each yellow line show attached fluid element to current Nastran mesh
Globally Mapping algorithms use some reference to limit the number of CFD mesh elements using this method
Depending on the length of the case, the reference length used in the algorithm can be changed from model size (by default)or average element size (good when dealing with wing)