Comparison of one-dimensional two-fluid models to predict two-phase gas-liquid flow variables in a vertical pipe and determination of an appropriate model

In this paper, an approach to the prediction of two-phase flows based on two-fluid models and conservative shock capturing method is presented. The advantage of this approach is that the interface is allowed to develop naturally as part of the transient calculation. Another novelty is the comparison of well-posedness criteria of three two-fluid models and developmentation of the single-phase numerical approach to the two-phase numerical approach. The well-posedness criteria for single pressure model is greater than free pressure model, and the numerical diffusion for single pressure model is little than two pressure model. It has been chosen 0.0000001, 0.000001, 0.00001, 0.0001 and 0.001 for pressure relaxation term in two pressure model 1. It has shown that by increasing pressure relaxation, the result of the two pressure model 1 and two pressure model 2 tending two each other, and this is a Confirmation of equality of pressures in two-fluid model 2.