2012
IMAACA 2012 Proceeding
Modeling and simulation of severe slugging in air-water systems including inertial effects
Authors: Jorge Luis Baliņo
Abstract
A mathematical model and numerical simulations cor- responding to severe slugging in air-water pipeline-riser systems, are presented. The mathematical model consid- ers continuity equations for liquid and gas phases, with a simplified momentum equation for the mixture. A drift- flux model, evaluated for the local conditions in the riser, is used as a closure law. In many models appearing in the literature, propagation of pressure waves is neglected both in the pipeline and in the riser. Besides, variations of void fraction in the stratified flow in the pipeline are also neglected and the void fraction obtained from the station- ary state is used in the simulations. This paper shows an improvement in a model previously published by the au- thor, including inertial effects. In the riser, inertial terms are taken into account by using the rigid water-hammer approximation. In the pipeline, the local acceleration of the water and gas phases are included in the momentum equations for stratified flow, allowing to calculate the in- stantaneous values of pressure drop and void fraction. The developed model predicts the location of the liquid accumulation front in the pipeline and the liquid level in the riser, so it is possible to determine which type of severe slugging occurs in the system. A comparison is made with experimental results published in literature including a choke valve and gas injection at the bottom of the riser, showing very good results for slugging cycle and stability maps.
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