Consequently, the flows considered here have some level of phase separation at a scale well above the molecular level.
Many texts exist that limit their attention in this way. One could classify them according to the state of the different phases or components and therefore refer to gas/solids flows, or liquid/solids flows or gas/particle flows or bubbly flows and so on. This still leaves an enormous spectrum of different multiphase flows. Consequently, the flows considered here have some level of phase or component separation at a scale well above the molecular level. For brevity and because they are covered in other texts, we exclude those circumstances in which the components are well mixed above the molecular level.
The term Multi-phase flow is used to refer to any fluid flow consisting of more than one phase or component.
