In dispersed phase flows one phase consists of discrete elements, such as droplets in a gas medium or bubbles in a liquid. The discrete elements are not connected. In a separated flow, the two phases are separated by a line of contact. An annular flow is a separated flow in which there is a liquid layer on the pipe wall and a gaseous core. In other words, in a separated flow one can pass from one point to another in the same phase while remaining in the same medium.