Distance between parent-child domains

[FOH]

Hey everyone I want to do a run using 2 nested domains, but I don't know if it exists any minimal distance between the parent and child domain boundaries. For example, in the attached image I have 2 domains, and the skyblue lines are the distances. Is there any good practice relationed with that?

 

[Ming Chen]

There is no strict rule how far the distance should be between parents and child boundaries. Usually it is fine if the distance is larger than 15 grids.