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Investigation of relative velocity in non-vertical air-water bubbly two-phase flows.

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Title: Investigation of relative velocity in non-vertical air-water bubbly two-phase flows.
Authors: Dix, Adam1 (AUTHOR), Kim, Seungjin1 (AUTHOR) seungjin@purdue.edu
Source: International Journal of Multiphase Flow. Jan2026, Vol. 195, pN.PAG-N.PAG. 1p.
Subjects: Relative velocity, Two-phase flow, Field research, Bubble dynamics
Abstract: • An experimental study of relative velocity in horizontal bubbly flow is performed. • Negative relative velocities observed and trends analyzed. • A model is proposed to explain these results, based on bubble wake interactions. • Applications to predicting gas velocities and improving CMFD are demonstrated. Gas-liquid two-phase flows are highly dependent on orientation, due to the typically large density difference between the phases. Most research, however, has focused on vertical flows, so fundamental parameters, such as the relative velocity, have received scant attention for horizontal or upward-inclined flows. This work performs detailed experiments in twelve horizontal bubbly flow conditions, measuring the void fraction, bubble velocity, and liquid velocity with local conductivity and Pitot-static probes. With this information, novel trends in the relative velocity are discussed. The relative velocity is found to be negative throughout the pipe, in contrast to vertical flow. It is found to be most negative in the bubble cluster at the top of the pipe, but remains negative even as the void fraction approaches zero. With the experimental database established, a mechanistic model is proposed for the relative velocity, based on the wake interactions between bubbles and liquid phase turbulence. The model is able to predict the presented dataset within 15 %. The gas velocity is estimated by combining the relative velocity model and a 1/7th power profile for the liquid, which allows for comparison against data in literature where no relative velocity data is available. The void-weighted area-averaged gas velocities then agree within 10 %. [Display omitted] [ABSTRACT FROM AUTHOR]
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Database: Engineering Source
Description
Abstract:• An experimental study of relative velocity in horizontal bubbly flow is performed. • Negative relative velocities observed and trends analyzed. • A model is proposed to explain these results, based on bubble wake interactions. • Applications to predicting gas velocities and improving CMFD are demonstrated. Gas-liquid two-phase flows are highly dependent on orientation, due to the typically large density difference between the phases. Most research, however, has focused on vertical flows, so fundamental parameters, such as the relative velocity, have received scant attention for horizontal or upward-inclined flows. This work performs detailed experiments in twelve horizontal bubbly flow conditions, measuring the void fraction, bubble velocity, and liquid velocity with local conductivity and Pitot-static probes. With this information, novel trends in the relative velocity are discussed. The relative velocity is found to be negative throughout the pipe, in contrast to vertical flow. It is found to be most negative in the bubble cluster at the top of the pipe, but remains negative even as the void fraction approaches zero. With the experimental database established, a mechanistic model is proposed for the relative velocity, based on the wake interactions between bubbles and liquid phase turbulence. The model is able to predict the presented dataset within 15 %. The gas velocity is estimated by combining the relative velocity model and a 1/7th power profile for the liquid, which allows for comparison against data in literature where no relative velocity data is available. The void-weighted area-averaged gas velocities then agree within 10 %. [Display omitted] [ABSTRACT FROM AUTHOR]
ISSN:03019322
DOI:10.1016/j.ijmultiphaseflow.2025.105529