Analysis of the Slip Relation Parameters in the Developing Region of Vertical Upward Two-Phase Flow With Co-Flowing Streams

The drift-flux model (DFM) is a powerful model capable of fast and accurate gas-liquid flow simulations. Its accuracy relies on proper specification of two empirical parameters of its closure relation known as the slip relation: C0 (the distribution parameter) and υd (the drift velocity parameter). The case of two-phase flow developing region where the dynamics of phase mixing can have an effect on C0 and υd has not been explored. The current study characterizes the developing region in terms of C0 and υd. For a variety of air and water flow rates resulting in either bubbly or cap-bubbly flow regimes, C0 and υd were measured experimentally using their respective definitions. It was found that both C0 and υd behave nonlinearly in the developing region, reaching an asymptote towards the end of it. The asymptotic values tend to match the ones commonly used for developed regions. The slip relation behaves linearly throughout the developing region, however the linear fit tends to underpredict C0 and overpredict υd.