A new model to predict the interface configuration, liquid holdup, and pressure gradient of gas-liquid stratified-wavy flow in horizontal and near horizontal pipes

Predicting the behavior of gas–liquid two-phase flow through horizontal and near horizontal pipes with low liquid holdup is an enormous challenge given the complex non-linear dynamical flow system. In this paper, we developed a new approach to predict the interface shape at steady or quasi-steady states based on the principle of energy minimization by highlighting the effect of the kinetic energy of both liquid and gas phases. The Kelvin-Helmholtz instability based on energy conservation, a dynamic instability concept, is performed to analyze the total energy involved in displacing the crest and wave properties of interfacial waves by considering the effect of gravity on the surface waves in the process of wave fluctuations. A new model for the interfacial friction factor is established considering the wave properties. Ultimately, a general mechanistic model of the gas–liquid co-current flow is established based on the above mechanistic investigations. The new model enables the simultaneous prediction for gas–liquid configuration, liquid holdup, and pressure gradient in horizontal pipes. The new model is verified and compared with existing models using experimental data from current study and stratified-wavy flow database. The results demonstrate that the new model is capable of providing satisfactory prediction for interface configuration, pressure gradient and liquid holdup for a wide range of operating conditions.