The paper analyzes the flow mechanism

shape characteristics and inner velocity distribution of gas-liquid slug flow in a horizontal pipe

and develops a physical model for the horizontal pipe.In a steady slug unit

lift velocity is always equal to shedding velocity

so the slug can keep an established shape.The model divides the slug into two parts:liquid-slug and film/bubble zone.For the liquid-slug zone

mass conservation and momentum conservation equations are built up to compute the local liquid-holdup and pressure-drop.For the film area

the model takes film height variation into consideration

assuming the height is only varying along the flow direction but not in the radial direction.The paper deduces a film height variation expression by building local control equations

and then develops a film height via liquid-holdup function and a film height via wet-diameter function.By comparing with test data and some other models

this model presents more accurate prediction results of liquid-holdup and pressure-drop.