In systems undergoing one of the species addition or removal processes mentioned previously, the addition or removal generates a mean flow in the flowing fluid as the fluid next to the interface is displaced by the production or removal of additional fluid by the processes occurring at the interface. The transport of the species by this mean flow is the Stefan flow.
When species are added or removed from a system, it creates a mean flow in the fluid adjacent to the interface. This flow results from the displacement of fluid caused by the addition or removal process at the interface. The movement of the species due to this mean flow is called Stefan flow.