Visualization and mathematical modelling of horizontal multiphase slug flow.

摘要

This study involves an experimental and theoretical investigation of slug flow in two phase gas-liquid mixtures. Water and an oil of viscosity 15 cP were used for the liquid phase and carbon dioxide was used for the gas phase. Flow in a 75 mm I.D., 10 m long acrylic pipeline system is studied. The techniques utilize digital image analysis and computational fluid dynamics. Flow is recorded on video by S-VHS cameras, using an audio-visual mixer. The image is then digitized frame-by-frame and analyzed on a SGI{dollar}sp{lcub}rm TM{rcub}{dollar} workstation. Detailed slug characteristics including, liquid film heights, slug translational velocity, mixing length, slug length, axial and radial void distribution, and instantaneous velocity profiles are obtained.; It is seen that slug characteristics are strongly influenced by the Film Froude Number ahead of the slug. The gas is released into the slug body in the form of pulses whose frequency increases with Froude number. The hydrodynamic boundary layer is destroyed at the slug front but begins to redevelop in the mixing zone. It becomes fully developed at the end of the mixing zone and the one-seventh power law shape is applicable. The length of the mixing zone is directly proportional to the Film Froude Number. At the end of the mixing zone, the gas tends to move towards the top of the pipe and the void fraction distribution tends towards a steady profile.; The slug translational velocity is described using a drift velocity model. A Froude Number for the slug is defined, utilizing the equivalent pressure head. The variation of the Froude Number in the slug is then tracked at different distances in the slug. The slug tail occurs as the Froude Number tends to unity. A model is developed to estimate the slug length. Agreement with experimental data is good. The model also closely predicts the data of other researchers.