| Two-phase slug flow exists in a variety of industrial situations. Its many important details are not well understood. In addition, little is known of the nature of churn flow which lies between the conditions for slug and annular flow. Both experimental and numerical approaches were used in this study to explore the hydrodynamics of slug flow and its transition to the churn flow pattern.; Extensive experimental data were taken using conductance wires, an electrochemical probe and a phase detection probe to simultaneously provide the axial void fraction distribution in the liquid slug, the axial profile of wall shear stress, the shape of the Taylor bubble, and the length and velocity of liquid slugs and Taylor bubbles. Data were collected for single Taylor bubbles rising in stagnant and flowing liquid as well as for continuous slug flow.; A numerical method was developed for computing the flow field in the liquid slug and the falling film around a Taylor bubble. The field is first computed with a designated rise velocity and shape profile. Then the shape is adjusted to satisfy a constant pressure condition at the free surface. It is shown that from an infinity of possible solutions the physically realistic Taylor bubble must have a rise velocity which creates a spherical nose in the vicinity of the vertex.; The combination of experimental measurements and the numerical simulations reveal the details of slug flow and suggest that a circulating eddy exists at the top of a liquid slug. In contrast to conventional belief, churn flow is found to be better perceived as an extension of slug flow, instead of a distinct flow pattern.; Numerical simulations for the flow around a single Taylor bubble give results in good agreement with the measured shape and the rise velocity of the bubble in both stagnant and flowing liquid for both turbulent and laminar flow. Similar computations for a train of bubbles show qualitative agreement with experiment. |
