In gas-liquid flows through tee junctions, because of the difference i
n inertia between the phases, the flowing mass fractions for an indivi
dual phase at the outlet sides differ from those at the inlet. This ph
ase separation is an important consideration in delivering fluids and
energy through pipe networks in the power and process industry. In thi
s work air-water and steam-water flows through branching and impacting
tee junctions are considered. Under certain conditions (when the volu
metric fraction of the liquid drops does not change appreciably and th
eir bulk density is much higher than the gas density, and when the flo
w rates and/or the gas volumetric fraction are high), these flows can
be approximated as irrotational flows of incompressible, inviscid flui
ds and are amenable to potential flow methods, for example, conformal
mapping. For the general case of gas-liquid flows through a branching
or impacting tee, a CFD code is utilized to conduct transient flow sim
ulations. Predictions of phase separation for both types of tee juncti
on agree well with experimental data.