The onset of gas entrainment from a flowing stratified gas-liquid regime in dual discharging branches

► Parametric experimental investigation of the onset of gas entrainment in single and dual discharging branches. ► Accurate physical descriptions of observed phenomena including the onset of gas entrainment and two-phase inlet regimes. ► Depiction of the observed modes of the onset of gas entrainment during dual discharge. ► Extensive data relating the branch Froude number, critical height, and inlet gas and liquid superficial velocities. ► Evidence of the effects of inlet liquid crossflow velocity on the onset of gas entrainment during single discharge.