The paper presents the numerical modeling of stratified flow in circular cr
oss-section pipe. Due to the geometry of this two-phase flow, the equations
of the problem are derived in bipolar coordinate system. Above the waves,
the gas flow structure is three dimensional, since secondary flows are indu
ced by the non-uniformity of boundary conditions related to smooth wall and
wavy or rough interface. The secondary flows being generated by the anisot
ropy of the turbulence, an algebraic stress model is used in the gas flow m
odel. The roughness of the interface is determined from experiments. Given
vertical profiles of longitudinal velocity in the gas and assuming a classi
cal logarithmic law above the waves, it is possible to determine the magnit
ude of the interfacial roughness. These experimental values are imposed in
the numerical simulations. Given these values, the comparison between exper
imental profiles and computed ones is shown to be satisfactory. Hence, the
simulations validate the concept of interfacial roughness to account for ga
s-liquid interactions. Finally, the interfacial roughness are non-dimension
alized following Charnock proposal and its order of magnitude to be imposed
in the numerical simulations is given. (C) 2000 Elsevier Science Ltd. All
rights reserved.