Abstract: | A physical model for the prediction of transition to slug flow is presented. The model assumes that the slug is formed as a result of a hydraulic jump which is sufficient to just touch the top wall of the conduit. This, together with a ‘breaking dam’ assumption at the rear of the slug, gives necessary and sufficient conditions for the formation of a stable slug. The minimum liquid film thickness ahead of the slug, degree of aeration within the slug and slug translational velocity are predicted. The predictions agree very well with those of previous workers and with experimental data. |