Numerical study of the influence of the internal structure of a horizontal bubbly flow on the average void fraction

This paper presents the results of a numerical experiment aimed to study the influence of the void fraction profile on integral flow characteristics of horizontal bubbly flows. To perform this analysis, a particular model which reflects better both the effect of non-uniform flow and concentration profiles as well as the effect of the local relative velocity between the phases than the well known drift flux model, was used. The relative phase velocity has been estimated by considering the movement of a single bubble in a liquid flow having a non-uniform velocity distribution. The analysis has shown that, in the case of strongly gravity-skewed local void fraction profiles, the volumetric flow quality β can be smaller than the average void fraction 〈α〉. This 〈α〉–β relationship is conditioned by the fact that the corresponding distribution parameter is less than 1, while the void fraction weighted average relative velocity of the gas phase is negative.