Computational modeling of bubbly flows in differential pressure flow meters

This paper addresses bubbly flow modeling within Venturi tubes and nozzles using the two-fluid model. The effects of non-drag forces as virtual mass and the so-called “transversal forces” such as lift and wall lubrication are investigated in the context of the two-fluid model. As expected, the transversal forces have an important influence on void distribution as long as the virtual mass affects the pressure drop along the contraction, which is the main parameter for the flow rate measurement. Models for the virtual mass and lift forces were implemented via user routines in commercial computational fluid dynamics (CFD) software, as the models embedded within these packages, specifically for virtual mass, were found not to be adequate for the purpose of this study. The models are validated against results from the literature and pressure drop measurements along a Venturi tube, developed in this work. Additionally, some experimental visualizations were used to make a qualitative comparison with predicted void distribution.

► Homogeneous model is not adequate to compute the pressure gradient in two-phase Venturi flow meters.
► Even using the two-fluid model, the virtual mass force must be considered in the balance for highly accelerated flows.
► Lift and wall lubrication must be included to correctly predict the radial phase distribution.
► The non consideration of the wall lubrication force could under-predict the angle for flow detachment, in the divergent section of the Venturi.