2015
IMAACA 2015 Proceeding
Linear stability analysis for severe slugging: sensitivity to void fraction correlations
Authors: Gabriel Romualdo Azevedo, Jorge Luis Baliņo, Karl Peter Burr
Abstract
In this paper a numerical linear stability analysis is per- formed to a mathematical model for the two-phase flow in a pipeline-riser system. Void fraction is a key vari- able, as it influences the mixture properties and slip be- tween the phases. In the model, it is assumed that an al- gebraic relationship exists between the void fraction and the state variables. This general representation allows to use empirical or drift flux based correlations. For a cor- rect prediction of the stability behavior of a pipeline-riser flow, preventing the occurrence of severe slugging, it is important to assess the sensitivity of the system response to different void fraction correlations. Three void fraction correlations are implemented Bendiksen (1984), Chexal et al. (1997) and Bhagwat and Ghajar (2014). The re- sulting stability maps and state variables profiles for ver- tical risers are compared for the different correlations. Results show that the different correlations give similar stability maps, with very small differences in the near horizontal branch (low gas superficial velocities) of the stability boundary and slight differences in the near verti- cal branch (low liquid superficial velocities). The differ- ent void fraction correlations show the right experimental trend by increasing the unstable region as the equivalent buffer length in the pipeline is increased.
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