Non-intrusive measurements in a dispersed, bubbly, axisymmetric jet

Document Type

Conference Proceeding

Publication Date

1-1-1997

Abstract

Measurements have been carried out in the developing region of a free, axisymmetric, isothermal, air-water, bubbly jet. Two experiments have been conducted at a fixed jet-exit Reynolds number and gas superficial velocity with two distinctive average bubble sizes. The volume fraction of the bubbly jet flow examined in this study is low and the resulting dispersed flow is dilute. A one-component Phase-Doppler Analysis (PDA) system has been employed to measure bubble-size and velocity non-intrusively. Two-dimensional mean velocities and three-dimensional RMS velocity fluctuations have been reported for bubbles. Axial mean velocities and RMS velocity fluctuations have been reported for the liquid phase. Our measurements show that differences in initial bubble-size, size distribution, and phase distribution influence the mean flow evolution, the fluctuation intensity of the carrier liquid phase and the RMS velocity fluctuations of the bubbles in the jet development region. The average bubble velocities are less sensitive. Bubble frequency profiles indicate that bubble migration both radially inwards and outwards occurs and that this trend is consistent with the measured bubble radial velocities. Bubble relative velocities are shown to deviate considerably from those predicted by steady- or quasisteady-state correlations. The observed sensitivity of the two-phase flow to size-related parameters and phase distribution indicates that discrepancies in previous measurements of dispersed, bubbly flows could be attributed to different bubble size characteristics, phase distribution, and/or initial conditions.

Publication Source (Journal or Book title)

American Society of Mechanical Engineers, Fluids Engineering Division (Publication) FED

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