Numerical modeling of wavy stratified two-phase flow in pipes

The paper presents the numerical modeling of stratified flow in circular cross-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 induced by the non-uniformity of boundary conditions related to smooth wall and wavy or rough interface. The secondary flows being generated by the anisotropy of the turbulence, an algebraic stress model is used in the gas flow model. The roughness of the interface is determined from experiments. Given vertical profiles of longitudinal velocity in the gas and assuming a classical logarithmic law above the waves, it is possible to determine the magnitude of the interfacial roughness. These experimental values are imposed in the numerical simulations. Given these values, the comparison between experimental profiles and computed ones is shown to be satisfactory. Hence, the simulations validate the concept of interfacial roughness to account for gas-liquid interactions. Finally, the interfacial roughness are non-dimensionalized 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.